I dug my FM out of the closet to see if I could be of any help. I found it still has film in it, so that is that, for now. ASA is set to 200, but seeing as how I haven't used it at least 15 years, and rarely shot anything that slow with it, I suspect it might be loaded with Ilford SFX. It might also be cheap color film. Obviously (?!?), it wasn't important enough to remove and develop. I probably have notes somewhere. Anyhow, I would advise against relying on the SN's on the pentaprism housing for anything important. Mine was replaced when the camera took a nosedive on tripod in 70 mph winds. Frankly, I'm surprised at how low this fully manual camera goes for. I wouldn't dream of selling mine, especially for virtually nothing, but then again, that does tell one how much 35mm is worth these days.