All original 1937 Bulova American Clipper. I'm not going to suggest a variant as we have no concrete evidence of an advert showing this exact combo with a variant. We have one advert showing as the "B" but that is also listed as having a white metal case back. Perhaps the "A" or generic AC was all gold plate/filled case and the "B" has a stainless steel back. Will have to check to see if we have any of these in the database.
Oh and the black leather cuff isn't original, just in case someone was curious. I've mounted the watch on this to give it more bulk as these early 20s/30s models are very small on a mans wrist.