This is a rock climbing nut that I found on Mt. Evans. This nut can hold over 2,000lbs and is just one small piece in a climber's arsenal among many pieces of protection. Somehow, whether it be "stuck", or maybe this person used it as a "bail" piece, it was left in the rock. I'm assuming the climber was unable to retrieve the piece. It was very hard to clean but I got it! Like finding a crisp $10 bill! (Price of piece) It's always fun to get free gear!