"1979-87: Steady Expansion Beyond Circus Circus

Slot machines remained a staple of Circus Circus's strategy to keep costs down and returns high. Unlike table games, the machines did not need casino attendants and were extremely inexpensive to operate. Furthermore, visitors found them unintimidating, so the machines typically had a high rate of use despite the fact that the house paid out a smaller percentage of winnings on slot machines than on other games. In 1979 Circus Circus purchased Slots-A-Fun, located next door to the first casino on the Las Vegas Strip, and a dramatic renovation of this once-ailing facility soon followed. "

So someone would have to do the research. Possibly something was in the building before that, maybe a small slot place, maybe something else and Sarno only bought the building.