Hard to judge the size........ But it looks like a horn cover to me. 1935-1938 Plymouth, Dodge, Chrysler, Desoto. Or......... Hudson? Anybody, anybody? Beuller? .
Looks like a jar of co****ly ground black pepper!........Oh, you mean the horn cover. Seriously, I really like the way you used the cover to create your tailight. It turned out great. Hot rodding ingenuity at it's finest.