Vintage Cadillac Motors Porcelain Sign. For sale is a Cadillac porcelain sign featuring an old car advertising for Cadillacs. Measuring at 12, this sign is the perfect size to display in your garage or man cave. This sign will enhance your mancave, collection, shop, or garage. It is your chance to own a piece of Cadillac advertising. 12 inches in diameter. Vibrant colors and excellent porcelain.