Is it a Clock or Watch?

[Ralph Porter]

I'm on the road and have just acquired a large ships' chronometer with gimbals, and in two wooden cases. According to winding instructions in the box lid and other markings, it is a Hamilton model 21. The dial is marked with N 5898 (serial no.?)and 1941 (production date?). The number on the movement is 2E5898. I believe it is a 85 size. I assume these are collectable, but how uncommon are they? Anyone know the production numbers? Shugart's book indicates they're pricey. This is an amazing industrial grade fusee movement! Inside there are three ports, one for winding and one for lifting/locking the balance wheel. I can't figure out the third one, located on the ratchet connected to the mainspring cylinder. Anyone know it's purpose? Any reference source info for this movement would be appreciated.
Thanks,
Ralph

[Ralph Porter]

I'm on the road and have just acquired a large ships' chronometer with gimbals, and in two wooden cases. According to winding instructions in the box lid and other markings, it is a Hamilton model 21. The dial is marked with N 5898 (serial no.?)and 1941 (production date?). The number on the movement is 2E5898. I believe it is a 85 size. I assume these are collectable, but how uncommon are they? Anyone know the production numbers? Shugart's book indicates they're pricey. This is an amazing industrial grade fusee movement! Inside there are three ports, one for winding and one for lifting/locking the balance wheel. I can't figure out the third one, located on the ratchet connected to the mainspring cylinder. Anyone know it's purpose? Any reference source info for this movement would be appreciated.
Thanks,
Ralph

[doug sinclair]

Ralph,

To the best of my knowledge, there were about 15,000 model XXI chronometers made. The 1941 represents the year that Hamilton was awarded the contract to supply the military with chronometers. The first one wasn't delivered for about two years after that.

You mentioned three holes in the brass case. You are correct about the one being for winding and the other being for locking the balance wheel. But you mention a third hole! I can only think that hole might be for the index screw that limits how far you can turn the back.

Are you referring to the fact that the chronometer has two winding arbors? The one on the mainspring barrel is used for winding the mainspring after servicing the chronometer. Thereafter, the arbor on the fusee is used to wind the chronometer. The arbor on the maispring barrel is not visible with the chronometer in its tub.

Congratulations on the find! I've enjoyed mine now for about 20 years.

[Don Dahlberg]

There were at least 8902 model 21s produced through during the war. The first was completed in Feb., '42. many more were made later. This is a fantastic accomplishment given that before Hamilton mass produced this model, chronometers were mostly made one at a time. Yet, this may have been the best chronometer ever made. The Elinvar Extra hairspring, and special balance made it very insensitive to temperature changes, one of the main problems to keeping good time.

There is a great deal of documentation still avaliable for this model. This includes reprints of military use and repair manuals. The repair manual is called "Overhaul, repair and handling of the Hamilton ship chronometer with parts catalog". Even if you would never repair it, it is good to read it. A more expensive alternative is the book, "The Ship's Chromometer" by Whitney and is published by AWI. It contains the same information and more on this and other chronometer. The NAWCC Giftshop carries the manual and both can be found at many horological bookstores.

It is a very fragile instrument and there are several don't. This includes, never turn the hands backwards!!! Also store it with a few winds on the mainspring. Storing it all the way rundown can be dangerous to parts and storing wound full will eventually set the mainspring.

I am confuse by what you mean by a third "port". Do you mean a third square end arbor that will accept a key? The one on the barrel is for setup after a repair.

The 1941 refers to the contract made between the military and Hamilton. Yours dates about Sept '44. If you are a NAWCC member, you can write the library and request the day of completion, and date sold for your chronometer. Just specify it is a Hamilton model 21 and the serial number. They also have the original card that recorded each step of production for your chronometer. They could photocopy this card as well.

Don Dahlberg

[Ralph Porter]

Doug,
Ah yes,the third winding location I mentioned is the arbor on the mainspring barrel. You're right, that one is not visible until the movement is removed from it's tub. There are only two holes in the tub bottom, and they are covered with a spring-loaded exterior plate. The works and both boxes are in great (but not perfect) condition and I'm really excited about finding this one.
Thanks, Ralph

[Ralph Porter]

Don,
I appreciate the great info and I'll hunt up a copy of the repair manual. Thanks for the precautions, I'll observe the "don'ts". I plan to have it serviced when I get back and intend to keep it running in my office. Obviously I don't know all the nominclature but the third "port" is in fact the key-operated arbor on the barrel. I guess I'll have to join the NAWCC, apparently there's a wealth of additional information available.
Thanks, Ralph

[Sheila Gilbert]

Ralphlporter,
That's a great idea, come on back and join us when you get back. I'm new to the NAWCC, but I'm sure that everyone here can give you more information than you can find anywhere else. This is THE BEST for Watch Collectors and Information.
Welcome!

[Don Dahlberg]

I finally got a chance to check the records. The last model 21 has serial number 2E13087 and was started on May 21, 1970. This does not count variations like the model 221.

Don Dahlberg