Bump r, If you go to the Quirks manual, the picture shows only the c above the 0/5 on the truck and trailer combination. The others do not show a c above.

Bill, cool pics. I've never seen it painted on the bumper. However I have read somewhere that in WWII the GIs were told to use whatever they could find like the bottom of a coffee can. I guess this was due to limited supply. Also, I wondered why your truck would have a six instead of the five. Only thing I could figure is if it were towing something other than the 3/4 ton trailer like a 1 1/2 ton trailer or something. Cool pics though, post more as you find more markings. Dave