This Bulova has the Omega mark so that tells me it's 1930 or 1940. The 10AE movement shows courtesy of Dr. Ranfft from 1929-1940. I'm thinking it falls into the Albert family. It's too bad that the mainspring is broken because everything else seems to be operating properly. Nice balance too. Thanks for checking this out for me.
The lug to band transition is an optical illusion; the outer 2 rings you see in ads are part of the lugs, not the band ends. Lone Eagle is also noticeably smaller. Distance between crystal horizontals and case edge is greater on the Ambassador. Below is a side-by-side comparison.
Lone Eagle case on left and Ambassador on right. Easiest way to tell, besides lug rings is length of case not counting lugs. LE measures approx. 29mm, and Ambassador measures 32mm.
Here is a LE in my collection that had the lugs cut down to the incised rings to accept a wider band. I don't think that has been done to subject watch, based on the radius of the lug bends and no trace of the rings.
It does, however appear that the lugs on subject watch MIGHT have been modified slightly or it may just be camera angle.
OK I'm back to Ambassadore.
The advert below which shows both the Lone Eagle and Ambassador, shows the lug difference much better.
I think we need to re-visit the LE's and double check as I think some may in fact be an Ambassador.
Note the case to lug transition on the LE versus the Ambassador.