If the music store says it is in an unusual key, it may be a C melody rather than a tenor. It would be slightly smaller than the tenor, and pitch would match that of the piano (off one octave). Check out the pictures on saxpics.com and see if it matches what you see there. That may be some help. There are also some people here who know much more than I, and might be able to help if you could email them some pictures. I can't help with that, though.