Here's a pic a took awhile back of an older S curved upsweep arm with double supports.This light is mounted on the back side of the pole as the road curves.The previous pic shows this type of arm without the supports.
Off route 29 outside of my electrical territory there's some similar setup like this with the double supports...but only difference...is instead of the S shaped...they are straight mast shaped...Some of those can also be found in Georgia Avenue in MD too.
There's also lots of similar arms in the Toronto area too. The only difference with our arms is that the bottom bracing is thinner. The ones downtown hold quartz metal halide gumballs (previously incandescent) while the ones in the suburbs used to hold MV clamshells but now have various HPS cobras. They even left the ballast can on some of the poles.
Do you know what fixture this used to hold?