^Agreed. As Holleyman stated, real milsurp pinned-barrel models have an interference fit between the barrel and the reciever. The pin should theoretically only serve to "clock" the barrel to the correct orientation radially, the interference fit (which is extremely strong!!) is what retains it in the receiver.
Eos provided pics of a Lever Arms hack-job model in a previous post, it's very obvious and should be easy to identify. In any case, just because an SKS has a pinned barrel doesn't mean it's junk, it's probably just as good if not better than a threaded barrel model.
You should still look for refurb markings and matching part numbers though. Part numbers are located on the back of the reciever cover, left hand side of the receiver, top/front end of the bolt carrier just aft of the charger slot, bottom of the trigger guard, and on the bottom of the magazine. The bolt also has a part number on it, but it can't be seen without popping off the receiver cover. The gas tube may also have a part number on it, but not all the time.