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It's the cheapest version of a Honda gas station. The next step ups are LX, SE, and EX. I have no idea when it was made, but it was made to provide people with cheaper gas than the other stations. They sold liquid gas.

Sunray DX Oil Company, which refined and marketed gasoline under the DX brand in several midwestern states, and included several refineries including one in Tulsa that is still operated by Sun to the present day. This move expanded Sun's marketing area into the mid-continent region.

Sun Oil continued marketing its petroleum products under both the Sunoco and DX brands through the 1970s and into the 1980s. In the late 1980s, Sun began rebranding DX stations in the Midwest to the Sunoco brand and even introduced the high-octane Sunoco ULTRA 94 gasoline to stations in that region, but by the early 1990s, they pulled out virtually all areas in the southeastern US and west of the Mississippi, resulting in the closing and rebranding of service stations and jobbers to other brands in those areas, notably Sinclair in Oklahoma.

http://en.wikipedia.org/wiki/Sunray_DX_Oil_Company