I've been fortunate enough to have handled several pieces of antique armour. One thing I always look for is damage, it makes it all more "real" for me.
Bear in mind much of armour of the late 15th-16th centuries was hardened and tempered. Its very resilient. As such, most of the damage you find will be cuts in the steel, or cracking from impacts.
I handled a jousting helm which had cuts all across the visor and corresponding cuts on the forehead, so that the path of the lance was evident when it was impacting.
The Museum of Natural History in NYC recently had an exhibit on the horse which included a 15th/16th c. horse armour. I snuck my way around the backside and saw two real nice halberd/polearm strikes on the horses rump.
I tend to see damage on the knuckles of gauntlets as well which would make sense.
Grant