Usually pretty easy to tell if it was overstress or a previous damage issue. It doesn't take but about 2 nosewheel touchdowns during a porpoise event and the nosegear breaks right off the firewall on the next oscillation. I can't believe the people who would try to 3-point tricycle airplanes when I was flying. It just blew my mind how close they tried to get to the ground in a level attitude, trying as hard as they could to set up a porpoise.