That's a Bendix-Westinghouse air compressor driven by the grinder. They were used on trucks and buses. Some, like this one, have a little oil pump in there to lube it, some have an oil line from the engine and then drain back to the crankcase. This one has a water cooled head, some have fins and are air cooled. Frank
Thanks, I'm going to have to print this stuff out so I remember what the heck it is..lol another vintage slide
Looking again at the picture of the compressor, the can is the oil supply, no pump in this one. Gravity feed till the can runs out. then drain it back out of the petcock on the bottom and run it again.