XP-1 preceded Ilford XP-2. What you got must be very old, certainly more than five years out of date. Nevertheless, it may work just fine if it has been stored decently well. I've used a quite a bit of XP-1. The last time was just a couple of years ago - very outdated film stored in the refrigerator. It worked fine. The film is very similar to XP-2. The developed film appears to have a heavier mask, and the films is probably a bit less sharp the XP-2. It is still an excellent, very fine grained, sharp film. This film may require a formaldehyde based stabilizer as the last step in processing. If you have the film processed in a commercial lab, you can restabilize and dry the processed film. (That is you can restabilize if necessary. I don't know that this is absolutely necessary. Perhaps one of the color film process experts can tell us.)