A year ago I purchased an Omega bubble back with a 283 movement (and no original crown) at a flea market for $120 not knowing what was wrong with it, to my disappointment it was the hairspring and the balance staff. Now you might not think these parts are easy to find but believe me I spent much of the rest of the year looking for them. The balance stem is available and plentiful however the hairspring and balance in working condition is not. After calling and email many of the larger watch parts shops and going through ebay I thought all was lost and this watch would end up on Ebay as a parts/repair watch.
I finally as a last ditch effort started calling the smaller parts shops and to my surprise the wonderful lady that worked there cross referenced and told me that the 265 was compatible with the 283. But how is this so? these are two movements from different times and they look completely different. Well the 260 was the base movement for the 280 movement.
Anyhow once I got the part I had the watchmaker put it in and it worked flawlessly, the watch has lost 1.5 minutes in 24 hours but I think thats more of a low cost watchmaker thing.
Here are some pictures of the watch. It has a cool looking waffle dial.