I don't remember if I was looking for anything in particular, but I pulled a few cameras from the cabinet and started trying spools among them.
All spools from the following cameras fit one another just fine. The Canon spools are the most luxurious (they are very nice).
Leica IIIa, Leica IIIc, Leica IIIf, Canon IIF, Canon IVSB, Fed-1 NKVD, Mir, and Fed-3 (I think thats all I grabbed). I also grabbed a Zorki-C, Zorki-4, and some other Zorki (?) The Zorki spools would fit each other but not fit in the other bodies. Thus, there is something about Zorki spools that is different. This couldn't be new knowledge...did everyone already know this?
I couldn't find my Minolta parts, so didn't try that spool. My informed guess would be that it works fine among everyone but the Zorkis.