I've been buying second hand Rz67 lenses and cameras - now I want to add some backs. Some people advertise saying the seal/sealant might need changing what part is that?
If you examine the back, You should find foam around the edges or near the hinge & latch.
It's easy to replace just needs a little patience.
I'm not sure about the RZ but the RB has foam on the adapter where the film back actually fits.