If it were me I would tear it down and take a look inside, 35yrs old those seals probably need replaced! if the guns looks new it probably is! and not used doesn't mean anything, piston seals only have about a 10yr shelf life, JMO, I just got done tearing down R10 tubed HW98, yes I said R10 tubed HW98, this a hybrid rifle, R10 power plant everything else is off of a HW98, its also stroked and tuned with JM Hornet spring for an HW50, this is 1 of OC rifles, the R10 rifles have the screw off end cap, their easy to take down, I would use a JM kit and a ASA piston seal,
So.... I lucked into a Beeman R10 .177 at an estate auction. No info on use or history available other than what I can see. It has the San Rafael address, so I’m figuring’ ‘85 or ‘86. It is like new with no bluing wear or marks on the metal. One small scratch on the stock that, honestly, probably happened at the sale with people handling the guns. I don’t believe this was ever shot very much, if ever. This would jibe with some of the other guns in the sale.
The R10 was pretty well known for breaking springs. Myself, I'd shoot it long enough to see if you like it, and if so invest in a tune kit and some good moly lube. Or just shoot it till something changes. It may be fine for a long time. I can tell you from doing it, don't use a Vortek kit with the factory piston unless you are pretty handy with tools. The notch at the rear of the piston is stamped out, and deforms the diameter of the piston and the sleeve on the Vortek kit won't fit inside. You can fix it and make it work, but it's extra work. You also have to remove the piston liner and use the new style cocking shoe. A kit from Air Rifle Headquarters should drop right in as it is.