Hy-Score Model 811?

This gun has spent the last 35 years inside a gun case. I am hoping someone can guide me in the right direction before I ever consider firing it. What little experience I have with these European brake barrels, it has become quite clear their piston seals turn to mush over an extended period of time. 

1. Should I lubricate the gun and attempt to fire it? If yes, what all needs to be lubricated?

Or

2. Do I forget about it all together, assume the seal/seals are toast, and attempt to find someone who can work on these? If yes can someone recommend a source?

Thanks,

Marty

Looks like a Diana Giss rifle.  David Slade used to rebuild them.  Beautiful rifle by the way.

Lovely rifle! The HyScore 811 is a re-badged Diana model 66. It's quite a complex recoilless rifle, with two opposing pistons and timing gears (the small round housings on the sides cover the gears). And the OEM nylon seals in those do deteriorate over time - if it hasn't been used in 35 years, it should definitely be checked out.

+1 on Dave Slade in Tennessee doing the work, he's really excellent. https://www.airgunwerks.com/tunes.html

I will certainly get in touch with Dave.

Thank you Bob and Mike!

Many more photos of the 811 here;

https://www.tapatalk.com/groups/americanvintageairguns/viewtopic.php?f=405945&t=10167

@o7shelby D. Slade Minor Hill TN. He will take care of you.

Oh I should have read all, oh well.