I was told many years ago that the strip of plastic you get when opening a pack is a good guage! close action on plastic strip ,make sure it is not twisted, if you can pull it out you need action work.The hard part is finding a smoker nowadays
The position of the top lever is a reasonable wear indicator but not infallible.
My first break open target gun was a 20 ga. Citori skeet. I bought it new and still have it. Its had many tens of thousands of rounds thru it. The top lever is slightly left of center but it still locks up solid and there's no play.
My first break open trap gun was a BT-99. After countless shells had been run thru it, the top lever was still slightly right of center. It still locked up tight and there wasn't any visible play. However, on firing, the gun would pop open by itself. That was indicator enough for me.
I use my older BT for games,registered etc. Trap guns are not built for The heavy game loads 1 1/4 to 1 1/2 mags which I have put through mine over the years. I noticed some looseness on the fore end and top lever going to the left with overall looseness. I dropped it off to Browning while at the Grand. Picked it up the next day. Its nearly as tight as a new one and they only charged me $30. Try that with your K or P gun. Clyde Doll