I should also add, that at around the same time-frame (1939), Singer produced a tubular steel straight-leg industrial stand also. It was one version of the “convertible stands” that were both treadle and electric clutch motor on the same stand.
The power source could be changed quickly from manual to electric power by changing the pitman rod from the flywheel to the motor actuator arm with the aid of a 2-piece pitman rod. A tiny coupling nut was moved from one piece of linkage to the other, and back, as the power source was changed.
I need to get a better photo of it, but at least you can see that it has tubular legs. The electric clutch motor has been removed for this photo. It also has a 16" diameter flywheel.
CD in Oklahoma