Mobilgas pump sign. 1930's

The first Mobilgas pump signs were not shield-shaped but rather had a unusual "keyhole"- shaped tin lithographed design. I got this sign 6 years ago @ the 127 garage sale. Up until now didn't know much about it. Did some research and discovered more about this kind of rare sign. It's near mint condition with just a slight flaw. The sign is dated 1939 and the other shield shaped sign is dated 1947.
Oh yeah the Corvette gets Mobil 1 oil.... and only Mobil 1