Cal 501 with and without chronometer certification - are the parts interchangeable?

He folks,

I’ve got a 2852 that’s a bit of a project. It’s one of the earlier examples with a cal 501, not in running condition and with parts missing.

My assumption is that while the adjustment process was different, which was duly noted on the rotor, the other parts are interchangeable with “regular” cal 501s, is that correct? I’d then save the rotor and the serial as a bare minimum and would use a donor movement to complete it. Finding a donor 501 isn’t difficult - finding one that was chronometer certified much more so, hence the question.

Thanks a lot for the feedback!

The movements are technically identical, though obviously more time would have been spent adjusting the balance assembly on the chronometer version before it left the factory way back. Remember also that back then, these watches were poised by hand without the benefits of electronics and lasers. If you drop in any old 501 balance, it's unlikely the timekeeping potential from a regular "clean and lubricate" service will give chronometer results. A master watchmaker with an Omega parts account, however, can adjust any 501 to run well within COSC with basically no beat error given enough money, time and effort. Depends what you want to spend and what your expectations are, I think.

Cheers, I just had to know if they're technically identical, thank you! The act of bringing them together, the service and everything that's part of it I'll leave to my watchmaker and I'm not bothered about extracting the very last second out of it's precision. Yes, it was running within COSC specs 65 years ago, but I won't get cross with an old lady for being ever so slightly slower in that elevated age. 😉

All parts are identical. In fact. Parts are available from a number of 50x movements and including some 47x and 49x movements

DON

Thank you, that’s also good to know. I’ll start the hunt for those cals. 😀

Interesting that back then the same movement code had COSC/regular, I had no idea, assumed it was a 564/565 thing like the later family

This is your family by the way: http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&&2uswk&Omega_501

If it was me, I'd probably only target 501/503 unless I 100% know the exact part I'm looking for is identical 😁 (from past mistakes)

Yup, IIRC only on the earlier examples of the 2852/2853, the 2930 Grand Luxe and possibly some chronometer Seamaster examples, though, before they switched the Constellations to the 505.

Luckily, the regular 501 was probably the 50s omega automatic movement produced in the largest numbers, of at least it’s right up there. I’ve owned a few spare ones already and am not worried at all, they’re relatively easy to find. Don’t think it’ll be necessary to steal parts from a mere blood brother, I’ll find an identical twin to sacrifice. 😁

Parts lists, including for the 501, detailing part numbers and differences from the base movement, can be downloaded here:

https://www.cousinsuk.com/document/category/omega-movement-parts