Over the past 45 years the arsenal has repeatedly taken these rifles out of storage, cleaned them up, shot them, and made any necessary repairs. This is why it's impossible to get an unfired SKS.
Arsenal repairs are considered to be original rifles; personally, I'd be much more suspicious about what Century International might have done with some of these imports before they put them out on the market. What you got ain't nothing special; so, feel free, go ahead and shoot it.
You do know the protocol - right? Thoroughly clean all the grease off the gun. Pay particular attention to the bolt assembly - Which should be, ideally, disassembled for cleaning. Failing this, soak it overnight in white kerosene.
The first time you fire that, 'new' SKS, single load the rounds. Then double load and fire with a very firm grip on the rifle. If all goes well for the first dozen, or so, rounds then you can start triple loading and firing - All with a very firm grip on the rifle.
(Because gummed-up SKS rifles have a nasty habit of suddenly going full auto on ya!)
Lots of luck getting all that Cosmolene off. I use automotive engine degreaser, white kerosene, and lots and lots of paper towels. Use a straightened paper clip to clean out the gas port. It's summertime, now, so placing the disassembled stock, wrapped in paper towels, inside a black garbage bag and leaving it out in the sun will help leech out a lot of residual Cosmolene that has previously soaked into the wood.