I was given a 35mm half-frame camera (Tessina). It uses special film reels which must be loaded from a separate film source, bulk or canister. A dozen rolls of exposed film were included with the camera. There is no information on what kind of film is in them. I'd like to develop them for the previous owner of the camera. They were likely shot in the early 1960s. I developed film from one of the canisters in Pyrocat HD along with some TMax 400 I loaded and shot with the Tessina. The TMax 400 developed fine but the unknown film came out all black. This old film has a thicker base than the TMax 400. I thought that if the film was C41 it would probably develop OK in the Pyrocat to give a BW negative? If it was color slide film would it turn black using the Pyrocat? Not sure what to do next to figure out how to develop this old unknown film.
Thank you for your help.