Seen this guy's like a few times. Though I think this might be the only one we have in the database now. I'll have to look. As this is from 1936 and Bulova seems to have made two different versions for the watches during the late middle to late 1930's both engraved and unengraved with the same model name, I believe this is the "Handcock" engraved version.
Very nice example of some model Plainsmen. The case is a 1936 and the movement is a 1936. That would seem that it's a highly likely possibility that they belong together. The ad shows the Hancock had a 15 jewel movement. And yours has a 17 jewel movement. It may be some other model instead of Hancock. What are the crystal measurements?
I think it's a Cavalier case, no question. Either it was married to a Hancock dial/movement somewhere along the way or to Ken's point it just plain came that way ( could a watch maker inadvertently switched them?)
The challenge will always be how to accurately ID them for future reference. It really seems that, post this discussion, we might consider it Non-Conforming? I hate to split hairs but it really isn't a Hancock or a Cavalier. The actual jewel count might be overlooked as a movement replacement and I don't think that alone should impact an ID but the dial stops the show for me.