You can look at them and tell they aren't used by the finish. They also have very little helix so I assume they are a performance gear and I would expect a little bit of noise. When I mentioned looking at the other teeth, I was talking about the other teeth on the ring gear. As you rotate the gear set, it transfers marking compound to the pinion which, in turn, transfers it bock onto clean teeth on the ring gear. Look at that and see if it indicates what the contact area looks like.

You could also run the pinion in and/or out .006 or so and see if it runs the pattern up or down. You may have hit the depth right where it wants to be.

Used gears are a pain, especially if they aren't going back into the same unit they came out of. Once the backlash opens up, they're junk and not worth fooling with. I will on occasion use an economy gear on a mild application, but I will not use a Chinese gear.