Rare Fire Plug by Marcel Gillen Metal MG Brain Teaser Puzzle. Condition is used. Amazing mechanical puzzle by Marcel Gillen Metal MG Brain Teaser Puzzle. Consists of brass pins fitted into an aluminum cylinder made to resemble a fire hydrant. This puzzle is hard to solve but is very fun to play with. We haven't figured it out yet! Being sold As-Is - as pictured - unsolved (we don't have the directions for solving it). Thanks