This brand once blanketed the eastern half of the Mother Road from Illinois to Oklahoma. In the late 50s it was shortened still further to just DX. One of the final-generation signs survived along Rt 66 in Baxter Springs KS until around 2010 or so. It's pictured in another image.

DX was taken over by Sunoco in 1972 and the brand was later abandoned. This sign is outside a used car business. Scratches on the "D" indicate the tree needs trimming.