This one is a puzzle. Casing appears to be Senator, Radio City or Blackout, but black and gray face is one I have never seen in this style casing. It is a perfect match to the crystal opening. 8AM movement appears to be an uncommon one and not currently represented in the database. Recessed opening in case back is round and a perfect match to movement. Movement is double stamped 1940 and 1941. Case is yellow gold plate with a stainless back. Band is a replacement.
Case back is marked with serial number on one end and "Bulova Quality" on the other. No interior case markings besides a multitude of jeweler's marks.
Currently running and appears to keep time.