I have a doubt about this watch case that looks like the ones used by Waltham and Elgin.
Normally the case back is engraved Blancpain (example the case back of one of my old ones no 201xxx), but by doing some research I found on the Net identical pieces with the same neutral back.
Probably one of the last watch batches to be quickly assembled with the rest of the stock before Blancpain's production stopped. What do you think of that?