When were tapered elliptical street light arms first used? I have seen plenty of Westinghouse OV-12s, OV-25 Flatbottoms, and even a GE Form 400 on a tapered elliptical arm.

Where I live, there are 2 types of those arms, Galvanized steel and aluminum. I have a few Sylvania 6 foot ( RE6MA) aluminum arms. They are nice to install. The galvanized ones are somewhat heavier.