Modelo Martha Washington com caixa de 1939 (ver imagem) e movimento de 1937 (seta). CAIXA: RPG 10K com 2 diamantes. Dimensões: largura sem coroa 16 mm; comprimento com asas 25,4 mm. BRACELETE: Metálica 12KGF. B/R. Pat. Pending com báscula. ESTOJO: Original Bulova Martha Washington em veludo verde. Não tem documento.
posted in 16.10.2012
Jose The small shield-like symbol on the back of the case (at your red arrows) is seen on many cases from this time period. It's not a date symbol. The case serial number dates the case to same year as movements: 1937. Looks like the original bracelet too! Snippet of 1939 ad below.

Martha Washington from me.
"
1937 Case and Movement, great box.
Yeah, an easy one. Marth Washington.
3 ticks from me.
Martha.
Martha. Always liked that name.
1937 Martha Washington...and a beauty at that Jose!
I didn't check all the ads to see if this Martha Washington could be ID'ed to a variant. There's this ad snippet below, from an "identical" Martha Washington "D" pictured below ad. The watch below sure looks like subject watch:


Subject watch now looks like a Martha Washington "D"
Nice catch Will, I'll take the"D" variant please.