If you're wondering how tough Perma Fin really is, let me cite another example.
The Winchester Model 94 has a safety catch designed to prevent the gun from firing unless the lever is completely closed. When the lever is fully closed, it presses upward on a small round steel part that sticks down through the lower tang. If you are at all familiar with Winchester Model 94s, you know what I'm talking about.
On this particular gun, the safety catch is made of very hard steel. Over the years it has peened the bottom of the lever because it's that much harder than the lever. Because of this I had some concern about how the Perma Fin would fare when faced with repeated contact with the safety catch.
During assembly, I used a small file to debur the lower end of the safety catch, to remove sharp edges that would make it more prone to cut through the Perma Fin finish. And so far, so good - there's no sign that the Perma Fin is going to be marred by it anytime soon.