I have been given my Grandads old Airsporter he bought in 1958, the box was really tatty so I threw it away and it now has a nice home in a sheepskin slip.
The bluing was nearly non existent and the power was at about 7ft/lbs and the stock was really dirty. I have managed to get it apart, the piston had a weird conical head which had broken down, but a mate knocked up a replacement on his lathe out of PTFE.
I removed all the rust with a flapper disc on my grinder, then polished it up with 0000 wire wool, there were some deep pitts so I filled them with plastic paddeng, smoothed polished it again, gave it a few coats of gloss black and it's looking OK.
The stock was a bit of a challenge, getting all the grime off was hard and I gave up, in the end I just rubbed it down with sandpaper and lifted the dents with an iron untill it was smooth, there was a weird sort of ES/ marked on it, or something but that has gone now, looks much better. A few coats of woodsatin and varnish, looks great!
The only real bit of trouble I had was with the stock bolt, after I had dug my way into it, I managed to get it out but the threads were damaged and the head will not take a screwdriver again. I overcame that by using an M8 tap, then making a new bolt from threaded rod.

All in, an enjoyable little project, I think I'll give my father-in-laws tatty MkIII a go next, I'm sure he would like it to have a little touch up after all the years he has had it.