As mentioned above, the 680 series Beretta guns have conical pins that engage holes in the barrel bolsters. As the gun is opened and closed over time the round holes become edge worn and begin to assume an oval shape. The bolsters are actually replaceable on the competition quality guns, but not on the lighter sporting models. I shot a tubed 682 in competion for a couple years and the condition of the breech face and those holes was thought to give a pretty good indication on how heavily a gun had been used. Although I never bothered with it, in the case of a Beretta O/U, there might be something to be said for closing the gun and then releasing the top latch.

A Springer Spaniel, a 6# double and a fair day to hunt.