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What theoretical advantage, if any, does a duo-in-uno hairspring possess over a helical hairspring?

Incroyable

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When they were in use specialists made them. A. P. Walsh and Hammersley probably made the majority between them. In Mercer's book on Frodshams he lists the chronometers with 3rd party maker's names made for Parkinson & Frodsham. https://awco.org/present/SamHammond.pdf

In some instances Walsh only provided the hairspring, in others he finished the chronometer and in a few he also did the adjustment for trial. I am pretty sure that Hammersley's business must have operated the same way.

If the market for these were small enough, it would have been difficult for others to compete with two top level artisans although many at that period of the last half of the 19th century were probably quite capable.
According to the Frodsham chart, Walsh only made 104 duo-in-unos over the span of 34 years for Frodsham.

This must mean these were tremendously expensive back then. So if I'm to understand correctly, the duo-in-uno was essentially for those who wanted a thinner pocket chronometer.
 
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Clint Geller

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Its advantage was that it gave similar performance to a full helical on a thinner watch. With modern computer aided design flat springs have the same performance so there is no performance benefit, although in contemporary horology that is no reason not to use it. Its operation is lovely to look at.

Two watches with this spring went to the open Geneva trial in 1876 and did very well.
It is true that as David Boetcher relates in his previously discussed article, in March 1860 Hammersley "announced" that he had invented a " 'doube flat isometrical balance spring' for watches' " [what we now call a duo-in-uno hairspring] "which had all the advantages of a helical hairspring but without increasing the thickness of the watch." However, the performance advantage Hammersley claimed for tria-in-uno hairsprings, and by extension, his slightly later duo-in-uno hairsprings, was that they eliminated, or at least minimzed, the break-in period of rate acceleration experienced with simple helical hairsprings. It may be that moderm computers can get a flat hairspring, made of modern materials, to give the same performance as any other shape of spring, but in terms of the springs that could be made by 19th century watchmakers, I have seen no evidence that Hammersley's performance claim for duo-in-uno hairsprings was either invalid or disingenuous. Furthermore, the early rate acceleration problem has to do with changes in the properties of the spring metal and possibly, changes in terminal curve shape during service. So while I can certainly believe that a computer can find a flat spring shape that is theoretically isochronous, getting such a spring to hold its shape and properties over time is another kind of problem entirely. Modern metallurgy is far in advance of 19th century metallurgy, but if 19th century watchmakers had had a perfectly time-invariant spring material or a perfect tempering process for making one, there would have been no "acceleration" problem to fix in the first place.
 
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According to the Frodsham chart, Walsh only made 104 duo-in-unos over the span of 34 years for Frodsham.

This must mean these were tremendously expensive back then. So if I'm to understand correctly, the duo-in-uno was essentially for those who wanted a thinner pocket chronometer.
Wow! I knew duo-in-uno hairspring movements were scarce, but I didn't know they were quite that scarce. I am very pleased to have acquired an example since this thread was begun. The watch is, in fact, relatively trim for a pocket chronometer.

watch front (2).JPG movement top side.JPG balance and hs close-up.JPG escape wheel and detent -2.JPG balance and hs -2.JPG watch front - bezel up (2).JPG rear lid interior w hallmarks (2).JPG Wilson movt -1 (3).JPG Frodsham PC case reaR.jpg case band and bow.JPG Frodsham PC case reaR (2).jpg
 
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gmorse

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Hi Clint,
However, the performance advantage Hammersley claimed for tria-in-uno hairsprings, and by extension, his slightly later duo-in-uno hairsprings, was that they eliminated, or at least minimzed, the break-in period of rate acceleration experienced with simple helical hairsprings.
I think the claimed advantage was less related to the precise shape of the springs than it was to the method of hardening and tempering them with the terminal curves in their final positions. This eliminated the need for these curves to be formed post tempering by bending, the common way of forming them, which appeared to be the cause of the change in behaviour of the springs over their first year or so in use.

Regards,

Graham
 

Clint Geller

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Hi Clint,


I think the claimed advantage was less related to the precise shape of the springs than it was to the method of hardening and tempering them with the terminal curves in their final positions. This eliminated the need for these curves to be formed post tempering by bending, the common way of forming them, which appeared to be the cause of the change in behaviour of the springs over their first year or so in use.

Regards,

Graham
Thank you for that clarification, Graham.
 

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Do we know if Hammersley made the spring for this Chas. Frodsham? (or the entire movement?)

The ebauche does not look like Walsh to me, but I suppose the hairspring could have been from him since there is no real way to tell.

Are Frodsham reported to have made any for themselves?
 

gmorse

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Hi Tom,
Do we know if Hammersley made the spring for this Chas. Frodsham? (or the entire movement?)

The ebauche does not look like Walsh to me, but I suppose the hairspring could have been from him since there is no real way to tell.

Are Frodsham reported to have made any for themselves?
He wouldn't have made the entire movement, (no single worker would have done), that would most probably have started life in one of the Prescot workshops, such as Joseph Preston, who supplied many of the great London firms. All the parts would have been made by specialists but some of the finishers would have worked for Frodsham or Dent exclusively; I believe Hammersley was an independent chronometer maker and more favoured by Dent for their best work, including pocket chronometers. He did also produce watches under his own signature although there are very few of these known.

I don't know whether Dent or Frodsham, (or anyone else for that matter), would have made springs 'in-house', but I suspect that to be unlikely, in view of the extreme segmentation of the watch trade.

Regards,

Graham
 

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Graham, it takes too many words to describe an English watch creation. The reference to Walsh was a reference to his escapement management. Is there a similar way to recognize Hammersley. As I recall you have handled some of those.

The only records I have seen are Parkinson & Frodsham with the several levels of Walsh work.
1668534133895.png
Walsh 312
 
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gmorse

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Hi Tom,
...it takes too many words to describe an English watch creation. The reference to Walsh was a reference to his escapement management. Is there a similar way to recognize Hammersley.
Indeed it does, but there was a strong traditional element in all this, and it's hard to distinguish between the escapements at this level from single photos.

The movement you've shown bears a very strong resemblance to an 1874 key wound Dent pocket chronometer with a duo-in-uno spring by Hammersley that I've handled:

DSCF5567.JPG

An obvious but minor difference is the escape wheel locking screw in the foreground, but I suspect that much of the similarity is due to the origin of the frame, in this instance Joseph Preston in Prescot. Do you know if they made your Walsh frame? It's also quite possible that the wheels in both these watches were cut by Richard Doke, regarded as the finest wheel cutter of his time.

DSCF5454.JPG

Regards,

Graham
 

John Matthews

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Graham - the frames look dissimilar to me, so I don’t follow your assertion that any similarity is due to the frame. My thoughts are that the machining of the frame would have been completed prior to being received by the finisher. To me the frames in detail, from what I can see from single photographs, appear to have been made to accommodate different trains.

John
 

gmorse

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Hi John,

I can see second, third, fourth and 'scape planted in the same relative positions. The third is planted in a 'bulge' on the edge of the top plate in both examples, and they're both half-plates. The detents are both in the same position, with the same foot and steady pin, and the steel shroud around the balance, which carries the detent banking screw is also very similar.

The unpivoted arbors will certainly have been planted by Preston or whoever made the frames, before reaching the escapement makers.

Regards,

Graham
 

John Matthews

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Graham - similar, but in my opinion, different ....

1668553526565.png


1668553451244.png


Tom's Walsh is slightly earlier I believe. Some of the components of the frames may have been made by the same workers, and also possibly both under the direction of Preston, but in my opinion to different calipers provided by different finishers.

John
 

Incroyable

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Does anyone have period price lists for a duo-in-uno pocket chronometer?

Given the small numbers made over the decades the prices must have been quite dear.
 

Incroyable

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Going over the AP Walsh chart, it's striking that he continued to make tiny quantities of these hairsprings over the course of three decades. To put it in perspective he started making duo-in-unos from before the start of the US Civil War up until the dawn of the 20th century.

Surely over all those years technology would have advanced that such a complex thing would been considered outdated? Who were these customers ordering 1 duo-in-uno a year?
 
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Tom McIntyre

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Sam Hammond bought a lot of them in the United States. Hammond may have bought 5 times as many as Parkinson & Frodsham based on this very small sample.
1668916132557.png
 

Incroyable

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They rarely seem to come up for sale though even in orphaned movement form.

Perhaps they were expensive enough that owners tended to prize them and were never really sold off for scrap later on.
 
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Hi Miguel,

Is your 1793 a duo-in-uno? It doesn't appear to be from the picture.

Regards,

Graham
No, has a "normal" hairspring. I found this one at a ridiculously low price, of course the case is not theirs, but it seemed such a good quality watch that I bought it immediately. I didn't know anything about AP Walsh or Hammond, until I read the information on the forum.
 
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Ethan Lipsig

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In post #17 I showed the "double-overcoil" spring on one of my Frodshams, about which Graham commented: "David goes on to mention Hammersley's design for a 'double flat isometrical balance spring' which corresponds exactly with the example shown by Ethan in post #17, and which was contested by J.F. Cole who stated that he had made such springs 30 years earlier, which Hammersley had subsequently to accept."

What was the perceived advantage of this spring design? Was there an actual advantage? How commonly was this spring design used?
 

Clint Geller

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Sam Hammond bought a lot of them in the United States. Hammond may have bought 5 times as many as Parkinson & Frodsham based on this very small sample.
View attachment 737161
There is at least one mistake in Gerit's table, Tom. I own Walsh for Hammond SN 263 and it has a helical hairspring, not a duo-in-uno.
 
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gmorse

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Hi Ethan,
What was the perceived advantage of this spring design? Was there an actual advantage? How commonly was this spring design used?
The object of many of these unusual balance spring designs was an attempt to reduce the problem of the spring not 'breathing' freely. The fact that the spring had to be attached to the balance staff at a point which wasn't at its centre of rotation, and attached to a fixed point at its outer end, meant that it was subject to varying radial forces as it oscillated. This made achieving isochronism, (the holy grail of watch designers), more difficult. Your example has an overcoil much longer than the usual 'Breguet' type, having almost two full turns above the plane of the spring, and this was presumably in an effort to allow the body of the spring to expand and contract with less interference from its terminations.

There are errors inherent in the basic design of the lever escapement, not all of which are related to the balance spring, which many ingenious makers strove to correct for years, with varying degrees of success short of complete elimination.

I don't think that any of these 'special' springs were in common use, being largely restricted to very high-class, expensive watches.

Regards,

Graham
 
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Tom McIntyre

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here is at least one mistake in Gerit's table, Tom. I own Walsh for Hammond SN 263 and it has a helical hairspring, not a duo-in-uno
Did the box come with it? Unfortunately both Gerrit and Bradley Ross who owned many of the examples are now gone.
 

Clint Geller

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Did the box come with it? Unfortunately both Gerrit and Bradley Ross who owned many of the examples are both now.
Yes, Tom. The box, and a possibly orginal chain, came with it. My key wound and set movement is front setting, which may be unusual, or at least, less common for Walsh. It was purchased at Jones & Horan.

Walsh box with watch and key.jpg Walsh Box.jpg Walsh Case Front.jpg Walsh Dial - 1.jpg Walsh Dial - 2.jpg Walsh dust cover.jpg Walsh interior of cuvette.jpg Walsh Movement.jpg Walsh rear case interior.jpg Walsh T-bar and Key.jpg Walsh watch and chain.jpg
 
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Clint Geller

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If we're to use the P&F chart as some sort of rough guide, then the duo-in-unos must have been a fraction of Walsh's production which likely wasn't very high to begin with.
If you were computing Walsh duo-in-uno hairspring movement production fractions rather than P&F fractions, it would probably be most informative to exclude the pre-1860 production from the count, as 1860 is about when duo-in-uno hairsprings first made their appearance. Taking Gerit's table as a guide, and excluding SN 263 as an error, Walsh's first duo-in-uno hairspring movement appears to have been somewhere between SN 264 and 284. Given the dates cited in the Boetcher article, I'd guess it was closer to SN 284.
 
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Incroyable

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If you were computing Walsh duo-in-uno hairspring movement production fractions rather than P&F fractions, it would probably be most informative to exclude the pre-1860 production from the count, as 1860 is about when duo-in-uno hairsprings first made their appearance. Taking Gerit's table as a guide, and excluding SN 263 as an error, Walsh's first duo-in-uno hairspring movement appears to have been somewhere between SN 264 and 284. Given the dates cited in the Boetcher article, I'd guess it was closer to SN 284.
It looks like Walsh was making on average 1 or 2 duo-in-unos a year based on both the P&F and Hammond charts. About half of them appear to be branded with his own name on the dial.

I notice there's one that is dated 1912.
 

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I notice there's one that is dated 1912.
Actually both A.P. Walsh and Sam Hammond were dead by then. I suspect someone found the material and decided to use it. Walsh had no offspring. I own that particular watch. Here is the page from my presentation on it.
1669004300539.png
 

Incroyable

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Actually both A.P. Walsh and Sam Hammond were dead by then. I suspect someone found the material and decided to use it. Walsh had no offspring. I own that particular watch. Here is the page from my presentation on it.
View attachment 737342
Do you think this might be a later recase?

Most of these duo-in-unos seems to have been marketed towards the wealthy rather than as tool chronometers.
 

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Do you think this might be a later recase?

Most of these duo-in-unos seems to have been marketed towards the wealthy rather than as tool chronometers.
It is possible but I do not think so. It "feels" like an inexpensive attempt to make the watch usable.

Hi Tom,


Do you know who made the frame for your #2036? I notice that it has an escape wheel lock.

Regards,

Graham
I have never removed the dial. Perhaps, I could work up my nerve to do so, but my hands which were never particularly steady, are less steady now.
 

gmorse

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Thanks Tom,

Don't go where you aren't comfortable, not with a watch as good as this!

Regards,

Graham
 
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Tom McIntyre

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It is a standard variant on watches with wind indicators. The normal hunting case configuration would have the indicator at12:00.

The McIntyre watches designed by Charles DeLong have the same feature. The McIntyre watches were made in 1911/1912.

1669088859876.png 1669088950322.png
 

Incroyable

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It is a standard variant on watches with wind indicators. The normal hunting case configuration would have the indicator at12:00.

The McIntyre watches designed by Charles DeLong have the same feature. The McIntyre watches were made in 1911/1912.

View attachment 737552 View attachment 737553
Yes I like the east west configuration. The usual of course is the north to south.

I'm also a big fan of asymmetric sub seconds dials.
 

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I have an interesting duo-in-uno watch.
Unfortunately an orphan, and in terrible condition.
Fascinating though.
Negus Brothers #5688. From around 1884, I believe.

All of the steel components have an interesting black finish that I've not seen before.
The screws, springs, all the motion work, the balance wheel and the spring, even the pinions and arbors have this peculiar black finish.
Looks like it was all powder coated or something.

The hairspring is very distorted, sadly. What has always caught my attention, besides the duo-in-uno, was that the spring is very thick. Almost square stock.

Regards,
Steven

20220218_152212.jpg 20220218_153614.jpg 20220218_153902.jpg 20220218_154146.jpg
 

Tom McIntyre

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I have seen a couple of these interesting blue steel watches. They are usually fire survivors that have been in a container while the building around them burned down.

The hairspring is interesting both for the form and the cross section. since there is no particular reason for the mechanics to be different. The flat hairspring normally seen gives more space to oscillate, but if none of the coils are in the same plane, there may be a functional advantage to leaving it round.
 

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Hi Steven,

That's definitely been in a fire, hot enough to create scale on the steel, so it will remain an interesting relic.

The hairspring is interesting both for the form and the cross section. since there is no particular reason for the mechanics to be different. The flat hairspring normally seen gives more space to oscillate, but if none of the coils are in the same plane, there may be a functional advantage to leaving it round.
It does look very similar to one I serviced a while ago, I think the increased length which this form made possible was enough to compensate for the practically square cross-section.

DSCF5465.JPG

Regards,

Graham
 
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S.Humphrey

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I have seen a couple of these interesting blue steel watches. They are usually fire survivors that have been in a container while the building around them burned down.
Hi Tom,

I had thought that at first, too. But after studying it a bit, I do think it is some sort of applied finish.
Firstly, I don't think you get that uniform black color just from heat, especially on intricate parts of widely various size and finish.
But, the best evidence I think is, if you look closely, the balance appears to be a "normal" bi-metallic compensated wheel. You can make out the distinct strips. Though, even the brass has been coated with the black there. It's the only brass bit that is blackened.
The black doesn't seem to have taken as well to the brass and bits around the edges/corners are flaking off. Maybe the expansion and contraction there. Not sure. It seems fine on the steel side.

In some places it does look very much like heat damage, but in other places it very much does not.
It's definitely something I haven't encountered before.
 

S.Humphrey

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Definitely a fire, huh?

ok. I guess I can believe that.
That is so weird though!
 
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gmorse

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Hi S.Humphrey,
Definitely a fire, huh?
ok. I guess I can believe that.
That is so weird though!
If the watch was in a container of some sort, as Tom has suggested, this type of surface degradation could be produced. It was clearly hot enough to distort the balance spring; fire can create some odd effects!

Regards,

Graham
 

S.Humphrey

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Hi S.Humphrey,


If the watch was in a container of some sort, as Tom has suggested, this type of surface degradation could be produced. It was clearly hot enough to distort the balance spring; fire can create some odd effects!

Regards,

Graham
Hi Graham!

Yeah. It is so weird, but as I look the glossy black parts that most look like a finish are the ones that would have had the best polish and the ones that are flatter black and less uniform are ones that would have been less finely finished. So it's making some sense.
Pivots were busted too, so I had presumed the spring was just mangled by some nimrod. I had only considered fire for a minute when I first looked, but it didn't seem to add up.
It would have to get very hot, right?
I expected more damage to other bits, like the gilt at those temps.

regards,
Steve
 

gmorse

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Hi S.Humphrey,
I expected more damage to other bits, like the gilt at those temps.
The mercury gilding on the plates is quite thick, and pure gold melts at 1064ºC, whereas scaling on heated steel can happen at rather lower temperatures; in any case, the plates are relatively large pieces. For instance, to harden many carbon steels they need to be red hot at around 770ºC, but scaling will often be apparent before this point is reached.

Regards,

Graham
 
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Tom McIntyre

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I had one of these that appeared to have been in a sealed container. The bluing/blacking was remarkable uniform and I managed to convince myself it had been done on purpose. I had Pat Caruso put it in running order and he dismounted the balance from the staff and found a silver ring on the staff where it had been protected by the balance hub.

It is possible that the person who had owned it before me had done some cleaning, but there was no vsible scale and the blue parts were pretty shiny.

My example was an 1899 model Waltham in AWWCo grade. I put it in a niello case and passed it on many years ago.
 
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S.Humphrey

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I had one of these that appeared to have been in a sealed container. The bluing/blacking was remarkable uniform and I managed to convince myself it had been done on purpose. I had Pat Caruso put it in running order and he dismounted the balance from the staff and found a silver ring on the staff where it had been protected by the balance hub.

It is possible that the person who had owned it before me had done some cleaning, but there was no vsible scale and the blue parts were pretty shiny.

My example was an 1899 model Waltham in AWWCo grade. I put it in a niello case and passed it on many years ago.
Hi Tom,

Thank you very much for pointing it out to me.
Now I know what a fire damaged watch can look like.
It is pretty amazing to me.
On most areas it is such a nice, uniform black, it seems easy to mistake for a deliberate finish.
The brass of the balance wheel also being black really threw me off when none of the other brass components show any sign of that.
As I've been reflecting on it, I suppose it must have something to do with that part being laminated to steel, but I have no idea how that happens.
Terrible shame to be lost in a fire. It has been a great study.


The dial, hands and case must have suffered a lot... Is this the reason why the movement is orphaned?
Hi Miguel,
I suppose it is.
None of those parts were with it.
 

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In the example I had the balance steel portion was also blue/black but the brass portion was not discolored that much. It may have been faded to a more yellow appearance but I cannot recall that well. (A long time ago.)
 
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