When modern octagonal-shafted poles, which are made of aluminum and are usually silver or gray-painted, first started appearing in NYC streets in 1950, the mast of choice was curved with a single thinner bracket, as shown here.
In the early 1960s when GE M-400s and Westinghouse OV-25s, which were oblong and gave a greenish white light began to appear (replacing the teardrop-style incandescents), a cobra-neck mast was deigned to support them, and the vast majority of the curved-masts were replaced with cobra necks, retaining the shaft. There are still about a hundred curved masts around town, like this one on White Plains Road in the Bronx.