The timers were quite often removed because it sounds like a bomb waiting to go off. When you push the coin plate in it also pushes a slide that then pushes the little tab on the side of the timer which has a clock spring inside. This closes a switch that powers the illumination and game contacts.. lights come on and you play. When the timer runs out, switch opens and lights go off... end of game!
Im surprised a game as late as 1947 still has this mechanism.. it really was mainly in 30's games. Even my 1940 Stoner Anabel had moved on from this.