Meaning a mechanically skilled person having appropriate tools can - if skilled enough - easily repair them.
Nikon Rumors shows a series of mechanical schematics for old Nikon F cameras: link
If you happen to still have one of these in your cupboard. Why not trying to disassemble and reassemble one?
It is fascinating that an all mechanical solution to aperture agitation synchronisation with shutter speed timing was precisely possible already ages ago.
Similar to the fascination of mechanical wrist watches which are miniaturised master pieces of mechanical engineering.
