In article <4a6gff$kce@sirius.intxpress.co.nz>, richard@nelson.planet.org.nz says...
>Can anyone help me please, I have a Nikkormat EL body in which the
>thin black foam strip under the hinge of the back is starting to
>crumble off. (rest deleted)

I have never figured out why some very old Nikons have foam in perfect condition, and others the same age (or newer) do not. Any ideas out there? Foam deterioration seems to be the only problem that old Nikons have that is related (somewhat) to age alone. You will probably find that the foam that the mirror hits is also deteriorated. I use thin
sticky-backed weather stripping from the local hardware store and cut
thin and flat strips for replacement foam (the original comes out with
repeated applications and removal of masking tape - a tooth pick can help you get into tight places). Mamiya replaces the foam in their
cameras cheaply - maybe Nikon does too? This doesn't answer all of
your questions, but.....,
Hope this helps.