The gmc cckw is a 2 5 ton 6x6 u s army cargo truck that saw service in world war ii and the korean war often referred to as the deuce and a half or jimmy the cckw came in many variants based on the open or closed cab long wheel base lwb 353 or short wheel base swb 352 initially all versions were of the closed cab design having a metal roof and doors with all steel cargo beds but as the war progressed an open cab version was designed that had fixed half doors and a canvas top