Please consider donating to help offset our high running costs.
Might not be the battery....
thanks so much.
I am so embarrassed, I have given you incorrect advise. I am sorry. 🤔
For some stupid reason I thought this was a F300. I blame my tiny screen phone. This movement takes a Silver Oxide 357 or 386 depending on which fits in the case. The 386 is a low profile version of the 286.
See: https://omegaforums.net/threads/omega-beta-21-battery-retaining-prong-screw-has-extra-spacer.95483/
I just had a 357 battery fitted in mine about 2 weeks ago and it was running about 40 minutes fast. It was keeping good time when laying flat on the sideboard but not when it was on my wrist.
After a bit of searching on the internet, someone who had the same issue swapped the battery for a 344 and the problem was resolved.
I have not tried it with mine as I managed to pull the crown out, so now I have to wait until I return to Europe to get it fixed.
I also read that there is a regulator screw next to the battery, but I don't think I would start buggering about with it. Leave it to the experts.