Dr. Nim is a toy invented by John Thomas Godfrey[1] and manufactured by E.S.R., Inc. in the mid-1960s.
It consists of a marble-powered plastic computer capable of playing the game of Nim.
The "game board" is based on the mechanical Digi-Comp II digital computer.
The fourth lever is the "equaliser" option; if set, the player can win if they play perfectly.
After the machine has played, the last released marble flips the switch back to end the turn.