Bold Art Deco therapeutic shocker with clockwork timer. This appears to be one of the first coin-operated machines made by LC Bradley, better known for his very successful Challenger drop case game.
The coin mechanism is really very clever: you drop the Penny which stops inside the lower mechanism, then by pushing the button all the way in it makes a bridge with the coin to push a ratcheting wheel. This starts a clock timer that counts down your use. Eventually a wire pulls down a Bakelite flap between two contacts and cuts the power. If the user tries to hold the button in to stop the clock counting down there is another set of contacts behind the button that cut off the power until you release it. Upon the button releasing, the Penny is free to drop to the cashbox. The allotted shocking time can be adjusted by the operator.