Rising Coin Castle by Mikame
MasterPiece from Mikame Craft.
You ask a spectator to sign a coin, and put this coin in the drawer at the bottom of the Tower. The coin visibly rises in the Tower's window! At the same time when the coin vanishes, a click is heard.
You have the spectator open the locked box at the top of the tower. Inside the small Locked Box is their coin! And yes the Tower's drawer is now empty!