Sinclair's HC gasoline was it's first superfuel. It came out in 1926. The H-C stands for Houston Concentrate, named after the refinery in Texas where it was fisrt developed. Some people prefered to call it High Compression but as per the book, "A great name in Oil, Sinclair through 50 years", it stands for Houston Concentrate
An HC truck door sign
One piece baked HC globe
A six foot DSP in the ring
I was told this sign was made for a Sinclair convention. It is not an old sign but still a piece of Sinclair history