Ok, First conjecture was possibly a Lone Eagle, then possible am Ambassador now we are strongly in the Unknown camp. Well eventually...
EDIT: 2012.08.26: Bulova Quality Pa. Jun.11.1927
The engraving is not present on the vertical sides of the bezel.
The bottom lugs are not the original configuration. The bottom bezel bar is covered & I can't see the chevrons. I can't see the top bezel configuration.
Lone Eagle series III movements are 15 jewel in 1931 & 17 jewel in 1933 as advertised. Below is a 1931 LE & ad for comparison.


I agree Wayne, Not a L.E. 21J might be an Ambassador or President?? Seems that Plainsman had a 2-tone case unknown like this awhile back.
Daca, What is stamped inside the caseback??
I will get that for you in the morning. I am away from the house for a few hours. Looking now at the 34 ad I see that it does specify 17J and not 21. i will change this to unknown for now.
I checked the inside of the case and it reads:
Bulova Quality
Pa. Jun.11.1927
1364860
Yeah, the swivel lugs are throwing me and the 1930 and 1934 President models both look to have engraving on either side of the crystal although they look to be the main model that came in 21j for this time period.
The presence of the hooded lugs says "Ambassador" all over it. That's where my vote would go.
The 1933 Ambassador bezel sides are engraved. The only 1932 ad we have is of the Lone Eagle. In 1933 the Senator & the Webster are the only stepped cases with no engraving on the bezel sides and are so thin that engraving would not fit, and the lugs are not hooded. Never saw one like this before. Baffling.
Yeah, when OldTicker asked about teh inside of the case back, I instantly had my heart sink and went "Franken". So was pleased to see the bulova inscription. I have been through tha ads from 1927 through 1935 and nothing I could see that was similar.
Unique is good but putting a name to the model would be priceless. BTW this is keeping good time even though the meter staff is almost to the extreme on one side.
In reply to Yeah, when OldTicker asked by Daca102090
The caseback markings looked like what you would find on the hinged Bulova's of the era, but I couldn't make it out. Just needed conformation....
Sooner or later an ad will surface to ID/confirm it as did the nice find that Shawn has added today...No more "Knotty Lug" Bulovas ;)
My vote is still Ambassador with or without engraving. I have this watch with engraving, all yellow gold case but logic would dictate it's a Ambassaor version just from the case design. JMO, Regards Shawn