tech talk: mystery rim

Yesterday at work, a co-worker brought me a wheel to inspect. It had come off a used bike we were overhauling for resale. He felt we should replace the wheel before putting the refurbished bike out on the floor, and I agreed. But he wanted to know if I thought we could re-sell the wheel as-is. The issue was a small hole in the rim.



The puncture had been made from the underside of the rim, and the wheel's owner had sanded down the sharp edges of the hole.

Looking at the damage, I suggested that it wasn't a great idea to sell the wheel with any sort of guarantee, even though the wheel was true and round and the Deore hub was in excellent shape. (I always tend to err on the side of CYA when it comes to things like this. I think my co-workers keep asking for my opinion because they think someday I'll let my legal paranoia down. It hasn't happened yet in my fifteen years at the shop.) However, it was unusual, so I asked to take a few pictures before he took the wheel away.

Turning it over, I saw the whatever had caused the puncture had poked its way through from the underside.





The consensus among those of us on shift was that somehow, a nail had poked through tire, tube and rim all the way, though it would have to be in the perfect position and the wheel would've had to hit it with enough downward force for this to have happened. I'd never seen anything like this before. Thoughts?