The GMC CCKW

Have a 1941 Jimmy (can be seen on this page ,Owners vehicles / modified CCKWs) that someone turned into a swamp buggy close to 50 years ago. This summer I replaced the cab and noticed an Emerald Green on the frame rails that looked like factory paint. I am aware that during production of the CCKW that some were used as Emergency vehicles and were painted a bright yellow (and also white I think) from the factory. But I cant figure out what this Emerald Green is all about, could this truck have been delegated to the Forestry Service perhaps? Obviously the unit could have been painted this color by someone owning the truck after its retirement from the Military but I dont think so. Did the CCKW share its frame rail design with a civilian cousin? as my truck was pieced together perhaps it has some such frame rail thus explaining the Emerald Green. Any Ideas anyone?

Only paint that I have ever seen under the CCKW WWII Factory OD finish on the Chassis is Black Chassis paint that was a standard industry practice. Got close to 60 years around them, and have seen some really fresh ones with factory finish. Most left the factory in OD color, even the red Fire trucks, and US Navy CCKWs showed OD under the finish on the sheetmetal.