I can't find any serial number on the tubing, just lugs. The non-drive dropout is stamped 1274 (upside-down 7) (sideways 99). Headtube lug is stamped 72.

Original posting has it assembled, but craigslist seller had pressed out the cotters, bending them in the process, and dis-assembled the drive rings because someone added spacers to work with that front Shimano replacement DR. The wheels had gone to another flip. It was marketed as a frame. I still don't think $30 is too steep.

I'll either have to source new cotters and learn myself some things about cottered cranksets, or swap for a modern version. We'll see. I have to get through the refurb on the trash-find PGN-10 first.

edit; photos