Originally posted by OldChE It looks like the PZ 28-105 is the lens pictured in the PZ-1p's manual. It is on the heavy side but I don't think that's due only to the PZ feature -- it also long enjoyed a reputation as being Pentax's best 28-105 optically (though I imagine the new D-FA 28-105/3.5-5.6 is probably better). There was also a (IMO inferior) Tamron rebadge non-PZ FA 28-105/4-5.6 IF that was sold for a while in between these two models.
The very light and compact FA 28-105/3.2-4.5 was a pretty late pre-film release, maybe shortly after the pretty-good FA 24-90/3.5-4.5 announced with the MZ-S?
There was also a similarly-styled FA 28-80/3.5-5.6 that I believe was also sold in MZ/ZX-series kits (including MZ-6/ZX-L) before the newer FA 28-90 mentioned above.
I think the FA-J 28-80/3.5-5.6 was probably the kit lens with the *ist film camera?