Philly's first mast-arms

[traffic light guy]

Philly's oldest mast-arm installations include, Econolite bullseyes, Eagle flatbacks, and Crouse-Hinds Type M and R signals. Now, I've been cavity searching the web for photo evidence. I watched mummers parade vidoes of new years 1971 and 1972, broad street appears to have no mast arms at the time. I can't find a single photo from 1973. The oldest mast-arm photo I've seen, was a B&W photo from 1974. Most of the signal brands included in these setups, however have already ceased production by then. The Eagle flatback ended production in 1973, while the Crouse-Hinds Type M ceased production in thr 60s. Help me please, this is very frustarting. Someone please clue me in on when Philadelphia, PA started to install their first mast-arms.