1879 SILVER DENT 61 STRAND POCKET WATCH WITH POWER RESERVE - INFO REQUIRED

[RAYLEE]

Hi All

I recently purchased this Dents pocket watch with London hallmarks for 1879. I was looking for any information regarding it. The case measures 60mm in diameter, the chain is off and there is a loose screw but the unusual balance spins freely when in place. Numbered 40587 as shown. I would also like some recommendations for a good watch repairer here in the UK.

Regards

Ray

 

[gmorse]

Hi Ray,

...the chain is off and there is a loose screw but the unusual balance spins freely when in place.

Do you have the balance cock screw or is it lost? The balance doesn't appear to be particularly unusual, apart from being almost fully populated with its screws, or are you referring to it being freesprung?

The dial seems perfect and I think the hands are all original. Was it sold as a lever escapement or as a pocket chronometer?

Could you post a picture into the edge of the movement, taken from the position of the case bolt, (at 6 o'clock), please?

Regards,

Graham

 

[RAYLEE]

Hi Ray,


Do you have the balance cock screw or is it lost? The balance doesn't appear to be particularly unusual, apart from being almost fully populated with its screws, or are you referring to it being freesprung?

The dial seems perfect and I think the hands are all original. Was it sold as a lever escapement or as a pocket chronometer?

Could you post a picture into the edge of the movement, taken from the position of the case bolt, (at 6 o'clock), please?

Regards,

Graham

Hi Graham

There is a loose screw with the watch but the circumference of the head

appears too small to me. I have included an image from the location you requested.
Regards
Ray

 

[gmorse]

Hi Ray,

Thanks for the picture, but what I'd really like please is a slightly lower viewpoint of the highlighted area, so that I can see the escape wheel region more clearly. Don't worry if it's a bit dark in there, I can probably adjust that here.



The screw in the images you've already posted is a pillar screw, which is just recessed in the cock foot and doesn't hold it down at all.

By the way, does the fusee chain have both its hooks?

Regards,

Graham

 

[RAYLEE]

Hi Ray,

Thanks for the picture, but what I'd really like please is a slightly lower viewpoint of the highlighted area, so that I can see the escape wheel region more clearly. Don't worry if it's a bit dark in there, I can probably adjust that here.

View attachment 740738

The screw in the images you've already posted is a pillar screw, which is just recessed in the cock foot and doesn't hold it down at all.

By the way, does the fusee chain have both its hooks?

Regards,

Graham

Hi

The end of the chain I can see does not have a hook on it I cannot see the other end it may be broken mid chain. The balance cock screw must be missing. I have included a few more images. It was bought purely as a pocket watch in a job lot. Also hope the new images help.

Regards

Ray

 

[Bernhard J.]

Wow, a chronometer escapement, now that was a brilliant buy!!! Hopefully the detent is still OK.

Cheers, Bernhard

P.S.: Remember never to attempt to remove the balance, if the watch is not completely let down. It is now, obviously, because of the broken chain. Just as a comment for the future when a new chain is on.

P.P.S.: Regarding your actual question, send it to Graham for service and repair and this extremely fine watch is in best hands!

 

[gmorse]

Hi Ray,

I have included a few more images. It was bought purely as a pocket watch in a job lot. Also hope the new images help.

Thanks again, Bernhard's comments are quite correct, what you have here is a freesprung pocket chronometer from one of the best London 'makers'. I put the term in quotes because it is the product of 30 or 40 separate specialist craftspeople.

Pocket chronometers, with the same escapement as their big brothers in boxes, mainly used in marine navigation, mapping and surveying, but in a size which could be carried, were always a very expensive item. They are, as Bernhard has pointed out, rather fragile and must be handled carefully and certainly not dismantled without a full understanding of their working.

The escapement in this form was developed by Thomas Earnshaw at the end of the 18th century, and its core component is a tiny sliver of steel, gold and ruby. This one is also from a Dent chronometer and the spring portion at the end next to the foot on the left is only about 0.04mm thick; this is very easily distorted or even snapped if not carefully handled.

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Regards,

Graham

 

[gmorse]

Hi Ray,

To give you some idea of what you have, see the beautiful 'Animating Time' video by the late John Redfern.

Regards,

Graham

 

[Incroyable]

Has the hairspring been replaced? It doesn't appear to have a helical hairspring.

 

[gmorse]

Hi Jeffery,

Pocket chronometers didn't always have helical springs. There isn't enough room under the balance cock on this example. A flat spring contributed to a slimmer movement.

Regards,

Graham

 

[Incroyable]

Hi Jeffery,

Pocket chronometers didn't always have helical springs. There isn't enough room under the balance cock on this example. A flat spring contributed to a slimmer movement.

Regards,

Graham

I suppose that's why the duo-in-uno was invented?

 

[Bernhard J.]

Not really, that was an improvement to the helical spring with respect to the points where the hairspring ends are attached. Typically these points are at different radiuses. The flat part of the duo-in-uno is essentially a very elaborated endcurve for the lower end of the helical portion in order to attach the lower end to the balance arbor (hairspring roll). As a result the duo-in-uno hairspring "breathes" with better symmetry than many normal helical hairsprings (having sub-optimal endcurves).

That may allow making the duo-in-uno hairspring a little bit less tall, but you still need quite a couple of turns in the helical portion. In this watch a duo-in-uno hairspring would neither fit.

Best regards, Bernhard

 

[gmorse]

Hi Jeffery,

Another factor, not exclusive to the duo-in-uno format but claimed by Hammersley, was a method of forming the spring which didn't necessitate bending the terminal curves after the spring was formed, but instead as part of the same forming process, using a complex dismountable former, (effectively a stack of discs), for the hardening and tempering. The usual method at the time, of manually bending the terminal curves after spring shaping on a former, usually gave rise to a gradual change in rate over the first year or so of operation. With terminal curves, the ordinary one-piece former couldn't be extracted from the spring.

Regards,

Graham

 

[RAYLEE]

Many thanks for all the advice and information . The video was particularly good to see and gives me an understanding of what's hidden inside. It would appear that this watch needs to be treated to some TLC and made whole again. I have done nothing with it and thought best just to leave well alone. Bernhard suggested Graham who I assume is the gentleman that has provided me with much of the information regarding the watch. I suppose parts are hard to come by should they be needed and a few photographs probably don't provide enough detail to establish what is required and whether it can be made good or has been messed about with in the past. Or indeed if Graham is interested in carrying out the work. But I would be interested to see if it could be done.

Kind Regards

Ray

 

[gmorse]

Hi Ray,

I have sent you a Conversation, (Private Message).

Regards,

Graham

 

[gmorse]

Hi Bernhard,

Remember never to attempt to remove the balance, if the watch is not completely let down. It is now, obviously, because of the broken chain. Just as a comment for the future when a new chain is on.

If the watch has maintaining power, it will still run with a broken spring, albeit not for very long. The watch which that detent in post #7 belongs to was sent to me because 'it wouldn't run for more than five minutes'; it transpired that the spring was broken near the centre and it was running solely on its Harrisons power. If I had assumed that there was no residual power left on the train and then removed the balance, you know what the result could have been!

It's a reason that some chronometers now have steel locking stones rather than the proper rubies.

Regards,

Graham

 

[John Matthews]

These facts cause me concern ...

the unusual balance spins freely when in place.

the missing cock screw and the broken chain. Those three taken together sound like a disaster has happened, or is waiting to unfold.

John

 

[Bernhard J.]

Hi John,

If a chronometer escapement is completely without power (see Graham´s comments also), the balance will swing apparently totally free aside the actuation of the passing spring, which is almost not noticable. And if the cock is in good condition (the pins still well), the cock will be well "stuck" in proper position on the plate, without the cock screw applied.

As a notorious optimist, I hope that there is no desaster going to unfold

Cheers, Bernhard

 

[John Matthews]

Bernard - you will note 'when in place'. Time will tell.

John

 

[Bernhard J.]

As I said, I am a notorious optimist (until I discover a desaster)

A desaster would be, if the detent is missing. Having to fit a new jewel to an existing detent is high end watchmaking also, but by far more "easy" than having to make one from scratch. OK, a bent tooth of the escape would probably also have to be attended to.

Cheers, Bernhard

 

[gmorse]

Hi Bernhard,

OK, a bent tooth of the escape would probably also have to be attended to.

These escape wheels have quite robust teeth, much stronger than the English lever ratchet tooth variety.

I think you have to possess a good helping of hope to work on these elderly machines!

Regards,

Graham

 

[John Matthews]

fit a new jewel to an existing detent is high end watchmaking

such is life ...

John

 

[Incroyable]

Hi Jeffery,

Pocket chronometers didn't always have helical springs. There isn't enough room under the balance cock on this example. A flat spring contributed to a slimmer movement.

Regards,

Graham

I'm curious if pocket chronometers with flat hairsprings were considered "lower grade" than ones with helical hairsprings?

 

[gmorse]

Hi Jeffery,

Pocket chronometers by their nature were subject to the variations of position in normal use that box chronometers weren't, and since they weren't usually relied upon as primary navigational instruments, I don't believe the flat springs, when finely adjusted as they mostly were, would have been much inferior in normal use. Of course, if a box chronometer ever found itself in any position other than dial up, its custodians would have had more urgent matters to deal with than its going rate!

Regards,

Graham

 

[John Matthews]

Jeffery

To my mind grade is something I associated with American watches, about which I know little. If you lookup a serial number of an American watch it will invariably return a specific grade. For English watches the term is used in a more descriptive manner and for the majority of watches the description would not include a nominative grade.

What Graham's answer reflects is more a 'fit for purpose' assessment than a grade assessment.

It also reveals that you cannot use a single design element of a movement, e.g. the design of the balance, as a measure of the quality and performance of a watch. It is the summation of all the elements and the way that they are combined, finished and adjusted that governs the quality and performance of a watch, and then only when it is first retailed. Perhaps I am being a little harsh, but the impression I have is that the 'grade' of a watch has more influence on the price some casual collectors are prepared to pay, than the quality of an individual watch.

John

 

[Dr. Jon]

Has the hairspring been replaced? It doesn't appear to have a helical hairspring.

 

[Dr. Jon]

On balance springs
Until Kew tests began in 1885 There were no ratings except Greenwich trials, which did not test in positions.

Also, in 1791 Maskeleyn held an open trial for the chronometer for Bligh's second voyage.

Earnshaw won it with a tapered flat spring, Arnold's patent was still in force.


Earnshaw argued shape,flat or helical did not matter.

Major benefit of helical is isochrony, which does not get tested and does not matter if chronometer is wound regularly.

 

[Incroyable]

Jeffery

To my mind grade is something I associated with American watches, about which I know little. If you lookup a serial number of an American watch it will invariably return a specific grade. For English watches the term is used in a more descriptive manner and for the majority of watches the description would not include a nominative grade.

What Graham's answer reflects is more a 'fit for purpose' assessment than a grade assessment.

It also reveals that you cannot use a single design element of a movement, e.g. the design of the balance, as a measure of the quality and performance of a watch. It is the summation of all the elements and the way that they are combined, finished and adjusted that governs the quality and performance of a watch, and then only when it is first retailed. Perhaps I am being a little harsh, but the impression I have is that the 'grade' of a watch has more influence on the price some casual collectors are prepared to pay, than the quality of an individual watch.

John

Grading also seems applicable to Swiss watches where the degree of finishing is varied but quite obvious in their differences of quality.

 

[Dr. Jon]

The Swiss did some grade marking in several ways.

HIgh grade examples might carry a marking, "superior" or "extra" or "chronometer" or "First class Bulletin" or even "Demi Chronometer"

 

[Buffomarinus]

I just stumbled on this discussion while searching for something else... Wow! Graham thanks for posting the link to John Redfern's incredible animation.

What a treat for the eyes and mind!

Rob