The usual protocols apply with regards to screw heads etc - if they have been chewed up then likely some mungo has been inside. On cocking you should be able to see the breech seal and how new it is. Any debris in the loading chamber would indicate decayed/crumbling seals.
Are you buying in-person or online?

I *think* Lawrie Armatruda was the go-to man for servicing these, but not sure if that's still the case.

You may welll get a better and more detailed response in the vintage and target shooting sections of the forum.