I never thought much of Eagle Alusigs until I actually restored one. These are very definitely industrial strength signals with very stout and well fitting aluminum castings that actually have a somewhat graceful appearance from the sides and back. These were definitely serious contenders at a time when traffic signals were transitioning from 8 inch to 12 inch models.
The Alusig was well suited for mounting back plates. The signal had a good mounting surface for plates to attach using heavy hex head screws. (This signal is displayed without the back plate to get a better view of the signal design.)