Anyone know what type of electrical connection this is?

[napabill]

Similar to a receptacle I had installed at the winery where I worked. The county school district had a Crown school bus converted into a mobile classroom. I arranged for them to come once a week to give ESL lessons to any of the vineyard or cellar workers who chose to participate. I let them off half an hour early with pay and they put in a half-hour of their own time. The bus needed a 380V plugin, which looked similar to this but was 3-phase so it had one more pin.

[Maxroadster]

Quick comment - Living north of Albuquerque we are seeing more & more Film Production Companies coming through as well as their crews. These folks travel in some pretty sturdy rigs and most have some rugged satellite antennas stacked on top. I think I can safely state that these folks require substantial power and those plugs with their ratings would certainly supply their needs!

[Dave Johnson]

You are looking at a International Electrotechnical Commission (IEC) Pin and Sleeve Device.
IEC devices are manufactured by a variety of brands, and are designed to be interchangeable throughout this rock called Earth.
The particular one pictured is a 3 pole 4 wire grounding device, possibly 250/125 volt 100 Amperes, single phase, 3 wire. In non-technical terms, two hot conductors, a grounded circuit conductor (neutral) and ground pin. Very common in North America.
IEC Pin and Sleeve Devices are differentiated by diameter for amperage, color for voltage class, and the clock position of the grounding (or earth) pin.