Vintage Shell Gasoline Porcelain Sign. This vintage Shell porcelain sign is an excellent addition for a gas and oil collector and has the neat graphic of the Shell Rest Rooms lettering. The sign features the Clam Shell shape and the iconic colors of Shell Gasoline. Measuring at 11 3/4″ by 11 3/4″, this sign is a great addition to any vintage memorabilia collection. The sign is perfect for display in any garage, sign collection, shop or man cave and is sure to be a great center piece. Vintage Shell Gasoline sign. Thick porcelain on both sides. Vibrant colors and excellent porcelain.