Interesting one on IG: https://www.instagram.com/p/CW6j733rV6Z/?utm_source=ig_web_copy_link Zenith 146D movement which is also marked 285. I recall posting one at OF earlier but can't find it anymore
It's from our very own @CaptainWinsor and for sale here on OF too https://omegaforums.net/threads/zenith-146d-ug-285-18k-gold.139298/
Yes that is/was mine. Missed this thread. Sold to another member here. Movement not swapped out. Some were marked with both for whatever reason. The extract from Zenith put it at 1963 or 64
https://www.rescapement.com/blog/zenith-a271-chronograph-caliber-146 Interesting article on this topic. To sum up, movement maker Martel (later acquired by Zenith) supplied the same caliber to both UG and Zenith. UG signed the caliber as 285, while Zenith as 146.