Thanks for your reply.
Quote: It will fit as all Pentax cameras since the M series accept the same magnifiers and angle finders.
I've got the magnifier. It physically fits every Pentax SLR I've used, from the Spotmatic to the MZ-5n to the *ist DS, except for the MZ-6. It must be something stupid on my part, but unlike other cameras, there isn't a slot on the viewfinder to slide in the magnifier.
Quote: However, the O-ME53 can barely cover APS-C viewfinders, I doubt it will work on film bodies.
Yes, there is a warning on the packaging that it doesn't fit a "full-frame" camera, but from my experience it works just fine with the MZ-5n. The MZ-6 has an even smaller viewfinder than the MZ-5n, so I'd really appreciate using magnifier with it. I'd contemplate getting rid of the MZ-6 if I can't get the magnifier to work with it.