This 'white box' model kit was a limited production kit from Tamiya. The vehicle represents a U.S. M1025 series Armament Carrier. What makes this kit special from the general release U.S. Modern 4x4 Utility Vehicle is the fact that this kit come with an only an M60 general purpose machine gun and it has two unique set of decal options that are not included in the standard release kit #32567 U.S. Modern 4x4 Utility Vehicle w/grenade launcher.
I had identified two variations of this already limited kit. The first variation is the original limited release kit which has kit #89790 on the box top and side label. Here are pictures of the kit box top and end.
In the process of my collecting of HMMWV related kits and items, I came across this kit on Ebay in October of 2012. This differs from the kit above by having the 'Tamiya' autograph and red stamp on the box top. It also has its own kit #89790**1300