1930’s 1940’s ACCESSORY AUTOMATIC LOCKING GAS CAP FORD CHEVY DODGE RAT ROD GM. THIS IS A VINTAGE AFTERMARKET ACCESSORY LOCKING GAS CAP THAT I HAVE BEEN TOLD IS CIRCA 1940’s. THE KEY WORKS CORRECLTY TO LOCK THE CAP. “AUTOMATIC GAS LOK CHICAGO USA”. I DO NOT KNOW THE EXACT FITMENT SO HERE ARE THE SPECS. BACKSIDE INSIDE DIAMETER: 3 3/8. GASKET IS 2 1/4 ROUND. LOCK MEASURES 1 3/4″ ACROSS THE’EARS”. YOU WILL GET THE EXACT ITEM AS SHOWN IN THE PHOTOS. PLEASE SEE MULTIPLE PHOTOS FOR BEST DESCRIPTION.