Hi Joe. The pin sleeve Male cap looks like 50 amp three phase , 4 wire with ground( 600v). The transformer is a 30 kva which means there is a capacity of about 90 amps @ 120/208volt when powered by a 480 volt source.
These are used for many purposes. With the cord it looks like something portable was used like a lathe, Table saw, of a special piece of custom equipment.