I would check to make sure that it "snaps" into sharp focus easily across the zoom range and at different distances. I have an 883 (also bought secondhand, FWIW) and it never feels like I have to fiddle to get the focus just right. The scope's pretty durable, but if there's multiple scuffs it's always possible that it was dropped and knocked out of collimation.
That being said, the Kowa warranty follows the scope rather than the owner (at least as of a few years ago, according to some old threads and employees on here) so you should be covered. Only thing to keep in mind is that if the scope was originally sold in e.g. Japan, you'll still have the warranty but would need to ship to Japan for repairs. Not sure how to check this other than messaging Kowa with the serial number.
I hope it works out for you! It's a fantastic scope and you should have no regrets grabbing it.