Doug - The plates on the right are the originals Chevrolet attached to the truck from the factory, with the most important one as Kevin said being the original vehicle serial number plate that was spot welded to the cab door upper pillar post. Interestingly that one has extra characters stamped "C - 59 - 8" (I think???) which would not have been done by the factory.

The one on the upper right is the vehicle data plate which was riveted to the lower drivers side cab door door pillar. It provides details on engine equipment and paint codes, which in this case is indicated as "SPEC" which matches up with it being originally ordered/built to fill a DOD contract order using a standard military paint color.

The larger upper left plate, if from the original truck sold to the government, will have a serial number that matches the one on the original Chevrolet plate in the lower right. It also provides standardized DOD military specifications (MIL-SPEC) identification info to identify and track the vehicle through it's government owned life cycle.

The oval brass tag on the lower left is a mystery at the moment as the picture doesn't provide enough detail to define what all is on the plate. I can think of a few possible things the plate might represent, but would like to get a better focused and close up pic to see as many details as possible before trying to offer more on that. Perhaps you can get a better picture?

~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)