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
In reply to 1931 ad. Courtesy of Lisa at by bobbee
In reply to Look at the toning of the by bobbee
Just spotted the new ad myself, and even though there slight differences in the ad description, I think that the Edwin is dead on.
The Gold gold numeral dial was an option for the Lone Eagle of the same period and it looks as though the dial would have interchanged in this case and movement.
Either generic Edwin or Non conforming Edwin.
It would be interesting to get a better look at what "A new model slave bracelet" looks like.
I'm still unsure about a two-tone case, and the wording in the ad "...in White or Yellow...". What does "in white or yellow" mean if its a two-tone case? The areas on the horizontals which appear countershaded in the ad appear different than those in the subject watch.
If we are going with the overall case shape, number of side steps and horizontal steps/sections, then the watch and ad are similar in those respects. Lisa has an 1932 engraved example tentatively ID'ed as Edwin, and she notes the possible two-tone (and engraving) differences between her watch and the ad.
There could be a two-tone variant of the Edwin, and the areas of those two tones could be slightly different that the counter-shaded areas in the ad (btwn arrows) AND it could still be a version of the Edwin.... or it could be something else.
Its close enough for a tentative ID from me...but a matching ad would sure help :)