Found a pair of these at a price I couldn't resist... So they are on their way in the mail

Some of my friends when we where 13-14 had these (times were less complicated in the early 90's, and boys doing mischief were not looked upon as robbery suspects or terrorists yet), and I was a bit envious. So now I get to scratch that itch

The seals will probably be dried out or rotted, so I was hoping someone on here had done any work on these and could give me some hints on how to get them working, and which o-ring sizes they need?