This engine was manufactured by the Bates Engineering Company of Chicago, Illinois, about 1910. It is believed to be a 19 kW (25 shp) Model 2 B. The engine had automatic intake valves and mechanically actuated exhaust valves.
Matthew B. Sellers, builder of the first Kentucky-manufactured aircraft, flew his first quadraplane from 1908 to 1913 powered by various 2-cylinder, horizontally-opposed engines. This Bates Model 2 B was one of these engines.
This object is on display in Boeing Aviation Hangar at the Steven F. Udvar-Hazy Center in Chantilly, VA.