As pointed out, you may not be "harmed" by this at all -- clean it, and it is yours, as if you shot it once yourself. It is a long way from wearing out.
As others have noted, too, always check a gun before receiving it. Gosh, this forum sees a lot of complaints about S&W revolvers that were taken home and found to have "clocked barrels." That means the new owner didn't inspect the gun! And, if the new owner finds it unbearable, it means that revolver has to go back to Springfield, MA in hopes the factory can fix it right.
Even mail order guns can be refused if inspected before signing for them from the FFL. But the lesson learned is to inspect the gun and if it has a problem, e.g., it is dirty enough to suggest it is really "used," then don't accept it.
By the way, I bought a M&P9 from Bud's and it showed up in a box with a white number on it... and inside was a clearly used pistol that was marked "Sheriff's Office, Jefferson Parish, Louisiana." I refused to accept it and the FFL sent it back... Bud's made it right within a day or two. They apparently sent me a police trade-in gun, presumably because of an honest mistake. It can happen!