LOOK!! What is this for???

Thanks for the info guys. I just realized where this came from. My brother has a 68 Coronet R/T and this was in a box of stuff he did not want taking up space at his place. I may sell it off at some point to get some goodies for my 70 Swinger. For the time being its going to hang on the garage wall. The pictures I posted really make this cap look worse than it is. There is some very light pits in a couple of areas and a couple of small scratches on the silver paint. Other than that this look brand new. Thanks again for the help gang!!!
Chas.