This is my sandbox.

Leading United States manufacturers of slot machines in early 1960s
Manufacturer Location Share of market
Jennings & Co., a division of Hershey Manufacturing Co. Chicago 40%
Mills Bell-O-Matic Corp. Chicago and Reno 35%
Ace Manufacturing Co. Maryland 15%
Buckley Manufacturing Co. Maryland 5%
Las Vegas Coin Machine Co. Las Vegas 5%
100%