Found this one on eBay. It was relatively cheap so I took a chance. Identification has been a challenge.
The case is 10 K rolled yellow gold. The case back is marked Bulova on the outside as shown. No markings on the inside of the case back. The serial number is very hard to see but it almost certainly begins with a "6".
I may be missing something obvious but I can't find anything that looks exactly like this one. It looks like a standard kind of case for the time but the closest I can come to it is an Alexander. But it doesn't have the engraving on the bezel that the Alexander seems to have. I'd call it a Ranger if the crystal bulged out in the middle but it's straight as an arrow.