Lady Berkshire also shown.
In reply to I meant the base metal for by bobbee
During WW2 Bulova did use Sterling instead of brass for watch cases and the case back is usually marked 10RGP over Sterling.
Brass was on the Strategic Metals list and pretty much all of it was diverted to the war effort along with massive amounts gathered through recycling efforts.
Well Fifth, could that account for the dark appearence of the bezel of the black & white pics, and not enamelling? I've done enamelling in my dark past, and as I recall you need something to retain the enamel flow in the kiln, as the powder melts. Enamel powder is usually coloured glass, finely ground. I've looked at the photo in question closely, and can't see any retaining ring for the enamel flow on the watch. I would say tarnish, or maybe light conditions as mentioned earlier, but not enamelling.