Nice find! I think there still might be some of these left in rural Ontario but so far the oldest I've seen in the Toronto area are the curved double guy style.
My best guess the original heads were an 8-8-8 Econolite Groove-Back on the pole, and a 12-12-12 Econolite Bullseye overhead with an Econolite exposed Neon pedestrian signal. That was standard for So-Cal back in the day. With those signals on it, the mast arm probably dates back to about 1956 or 57.