Bob, That is a Truck, Utility, 3/4 ton, 4x4 M-1009.
The M-1009 is a Commercial Utility Cargo Vehicle (CUCV pronounced "cuck-vee"), a military modified Chevrolet/General Motors Model K10516 Blazer with a 3/4 ton rating. The CUCVs were an attempt by the U.S. military to use COTS (commercial, off-the-shelf) vehicles with minor modification in non-combat roles. This effort to save money was not very successful and eventually all CUCV units where replaced by HMMWVs.
The M1009 was produced for the U.S. military from 1983 to 1986. The M1009 differs from the civilian Blazer in that it has a heavier spring in the suspenstion and has no air conditioning. The electical system is a hybrid 12/24 volt, with most of the truck running on GMC standard 12 volt electrics, but the glow plugs, the starter, and the military slave cable jack are at 24 volts. The M1009 has a pair of 12v alternators and batteries wired in series to supply the 24 volt circuit. The glow plugs are standard 12 volt plus wired through a bank of resistors to run properly on the 24 volt side.
Dennis