Other than the fish scale Demaskeening, can anyone point out another very fascinating feature of this watch I recently acquired?

Steve

Is it the balance wheel?

Tom

Tom,

You are absolutely correct. It is an Elinvar balance and hairspring assembly in a watch that predated that style by about 20 years. Unless someone can show a memo from the factory saying these were upgrades or a prototype I'm going to feel like the horses behind. No wonder it kept such good time.

Steve

I dug through my "bunns" and found a 2 year later vintage 2875236 . . . .

That has the "conventional" wheel and spring. I am sure that yours was a (very good idea) "jeweler's upgrade". They are beautiful to behold in either condition! One other interesting thing about your elinvar conversion, the mean time weights appear to be screwed all the way in, or are not there.

Steven

Well how about that, I was kind of right. I noticed the balance wheel was different but I didn't know why, so now I learned something today.

Thanks
Tom
ps. Nice looking watch too!

HI Steve,

any chance of a close up around the balance area?

There was a similar situation that arose on a Sangamo Special that sold here on this site where it was discovered that it to had an Elinvar balance assembly in it and was the subject of much controversy but was later proven that it was more than likely an upgrade that could have been done only at the factory and the company memo to prove it was available. This may have been the case as well but I lean more to side of NOT!!!!. But this is hopefully an easy fix to put back if need be and I am left with a very valuable part for a 161 Elinvar if I come across one that has a standard balance in it. For now....it stays. And like I said, it keeps great time. I wound it for three days straight and never had to correct the time.

Steve

Chris,

You posted while I was writing but lets try this.

Steve, I think that to "reverse" the long ago upgrade of that beautiful watch which also would "reverse" the "Karma" of that watch. That is a great watch to enjoy, carry, and someday use to share the story of how these could have been upgraded when the opportunity presented itself.

Another thing yours and my watch both show is the peculiar "upside down" balance jewel screws that Illinois did for a few years. That yours remains as original says volumes about the professional quality of the conversion for more accuracy.

Dave,

I agree that it was something that had to have been done a long time ago and it is not hurting anything the way it is. Also, as optimistic as I want to perceive this, it may have been done by the original owner who dearly loved this watch (very easy to do) but yet wanted a top of the line timekeeper. Who today would part out a 161 or 163 Elinvar and put it into a 21 Jewel Bunn Special? With that being said, how many fish scale Elinvars are out there?

Steve

Great photo, I agree with Dave would leave it exactly as is, more of these will no doubt show up in the future.

I got a bunn special some years that was only missing the balance so I changed the stud and turned down the pivots on a 992B balance and fitted it to to get the watch going and ran very well. I also bought a late model 992 on ebay that somebody had dropped a 992E balance in,it's still laying around the shop somewhere and it runs well also.

Steve,
What a great post!
First, I love the fishscale damaskeening, and thank you for the chance to learn about the balance! Just love it!

A few lessons needed here.

I don't know about others, but I sure could use an example of just what makes an Elinvar and Elinvar, and what a standard one looks like.

By the way, Great Photos you guys

Sheila, I attach a picture of a "normal" Bunn balance wheel (that Steve just won on eBay) next to Steve's "improved" Elinvar Bunn type with a couple notes to help you understand the difference;

1. Non-Elinvar uses CUT wheel and uses Blue/Black balance spring; The wheel is "CUT" in two places around the periphery of the rim to allow the bi-metallic wheel rim to contract and expand with temperature causing the balance wheel to oscillate (spin slightly faster or slower to offset the OPPOSITE temperature effects causing higher and lower spin resistance of the balance spring which is Black or Blue steel in color.

2. The usually whitish color Elinvar Balance spring has imperceptible changes in spin resistance through the normal range of temperature, so there is no need to use a Bimetallic wheel with cuts for temperature compensation. Thus the Balance wheel is solid. Some were made with Invar, or similar super-stable alloys.