I have 6 inch steel wheels that came on the truck. these are 4 nub ,so newer, but the stamping is by the valve stem hole. yes its blurry but the digit on the left of the stem is a 6, and they are 6 inch. I had these sand blasted before powder coating them, so the stampings are visible, but not great. Might be they are there on yours if you get them blasted? I had no idea they were there until I blasted them.