i dont know alot about these tags,,they have been called aux. tags to inspection tags,,what i have heard is that the numbers an letters on them are just like the fender tag codes,,if yours has them try and see if they cross over to a fender tag code option,,i believe they were usally took off at the line were they were built,,as i said before it told the inspector something as it went down the line,,but i cant say that for sure,,just what i have been told over the years,,most of what i was told was that is about the engine but may have been used for other options,,but i cant give you any links to show this,,but since they were attached to the fender tag,one can only assume it was part of a describtion, of the car being assembled