I'm not an expert but I decided to poke around.

Robert Eisenstadt's mold project shows the Horsehead Right mold with a starting date of 1965.

Fuller's Index shows Hoot Gibson D-4-C Ranch as opening 1946 and closing 1951.

If the chip is real then my guess is that Eisenstadt is wrong about the date of the mold. Are there other examples of HHR prior to 1951?