From narwhalforall: A retired Lego mold. Retired after producing 120,000,000 bricks.
fuzzerton: I used to work for the LEGO group, and at least according to internal communication (propaganda?) they're so concerned about industrial espionage and protecting their patents, when a mold wears out they encase them in cement in the foundations of buildings that are being constructed. Somewhat doubtful, but I found it interesting nonetheless.