So far I've found an acorn jamming up the works
(!!) and lots of dirt,
An Acorn... What, a System 1, or an Atom, or a Beeb or an Arch, or what...
(sorry, couldn't resist...)
:-)
I have no idea how it got in there; there isn't really a sufficient gap
anywhere for such a thing to fall inside. And it was *very* well buried
inside the mechanism (almost as though someone stuck it in there for
fun!)