Here is a photo of an engine I have owned for several years. It was built by Hercules, for sale by Sears & Roebuck and under the Economy name.
The Model JK means it could be run on gasoline or kerosene. Except for two truck wheels and the pull handle, this is an all-original unit. It was so dirty when I bought it, I wasn't sure if it was an Economy or a Hercules (red or green paint, respectively).
It had been used as a compressed air source for spraying whitewash in barns so it was a rusty tanish-white color all over. With a lot of careful cleaning, this is the result.
The compressor makes about 50 pounds of air before it starts to slow the engine down. There is a stencil on the inner side of the truck rail that says "Gast Mfg. Corp. 331 Bridgman, Mich." Gast Mfg. Co. is still in business making air and vacuum pumps and has a plant at Benton Harbor, Mich., which is just up the road from Bridgman.
Gast Mfg. Co. probably built the truck as well as the air compressor, as I have never seen this style of wheel on a Hercules-Economy truck.
I am sure this engine must have been advertised by Sears in its catalog in the early 1930s, but so far I haven't been able to come up with that information.
4814 47th Ave.
Kenosha, WI 53144