I bought this sign at Iowa Gas the other week.
I was told it was probably used in an oil can rack. Dad has a can rack in his collection that did not have a sign on it so I took it out to his place to see if it would fit. It looks like the sign was originally used in a rack like this.
I still need to get a piece of metal made to hold the sign in place. The rack already has two holes I can use to fasten it all together.