The earliest known coin-operated computer or video game, Galaxy Game, was installed at the Tresidder Union at Stanford University in September, 1971, two months before the release of Computer Space, the first mass-produced video game. Only one unit was built initially, although the game later included several consoles allowing users to play against each other.
"The game was programmed by Bill Pitts and Hugh Tuck. Like Computer Space, it was a version of the existing Spacewar!, which had been created in the early 1960s on the PDP-1 and ported to a variety of platforms since then. The coin-operated game console incorporated a Digital PDP-11/20 with vector displays. The hardware cost around $20,000, and a game cost 10 cents or three games for 25 cents. In June 1972 the hardware was improved to allow the processor to power four to eight consoles. The game remained popular on campus, with wait times for players as much as one hour, until it was removed in May 1979 due to damaged screens.
"The unit was restored in 1997 and now resides in the Computer History Museum in Mountain View, California" (Wikipedia article on Computer Space, accessed 08-26-2009).
Lowood, "Videogames in Computer Space: The Complex History of Pong, " IEEE Annals of the History of Computing 31 (2009) #3, 5-19.