Sort of looks like a His Ex C.... but 10 years earlier and littler.
Sporting a R/R Band that's era.
Geoff has an unknown on site here:http://www.mybulova.com/watches/1940-unknown-2476
DarHin got Geoff's crystal dimensions and found that 1943 GS crystal catalog has an MX318-25 20.6x15.6 which "fits" and names the model as "Winston". Rocket Cylinder Crystal catalog No. 9 also shows a Bulova Winston w/ similar dimensions (below)
Neither Rocket nor GS crystals give Bulova model number w/ crystal number/details. SUC conversion chart doesn't cross list the RMS 122-5 nor the GS MX318-25 for BB, or AM PerFit. Too bad, because if one of the crystal catalogs also gave a Bulova model number, we'd have another method to confirm the two Crystal fits the Winston. JP noted the models lists may be useful for this cross check. Good thinking JP!
The Bulova model lists show a single "Winston" w/ unique model number 38777. Maybe someone has a different crystal catalog which includes the unique Bulova model number and the Winston model name? Or it would be just as informative to find out this unique model number fits something other than the Winston.
The two crystal specs are a good tentative ID. It would be a stronger tentative ID w/ model number to crystal ID. ..but w/ no ad, still only a strong tentative IMO.