Hard Boiled Quarter
Hard Boiled Quarter (or Half Dollar) was a product created by Paul Harris and Mike Caveney marketed by Johnson's Products (at least by 1988) as a version of Harris' Torn & Restored Coin routine which was originally published in Supermagic (1977) and later revised in Art of Astonishment Vol. 1 (1996)
A quarter is held over the flame of a lighter to "hard-boiled" it. The magician proceeds to crack the coin into three separate pieces. The three pieces are stacked together and the spectator's finger tip is placed on top. The lighter is now used as a welding torch and when the spectator lifts his finger, the three pieces instantly and visibly restore into its original unbroken form.