First up we have General Railway Signal's three lamp traffic light style signal. Previously GRS has been the leader in modular signal design with their Type D signal having one lamp and the ability to be stacked as high as needed. Seeing US&S with its successful 'N' series of linear multi-lamp signals, GRS added this rather low cost clone to its lineup. Can you can see from the photos it was very low frills except for a snazzy block style GRS logo on the back. The only nod to progress appears to be rust resistant aluminum construction.
These signals are quite rare with the only notable installation being the LA Union Passenger Terminal and this attests to their general success in the market. It seems that GRS was stung by this turn of events as they basically exited the market for signal hardware aside from long running line of rapid transit signals that continue to be sold under the Alstom brand.
As I said before, US&S took the opposite lesson and decided to add a modular signal to its lineup to supplement the N series that was forced to use a round marker lamp for single light situations. What they came up with is best described as...bizarre.
Yes they thought the best solution for a stackable modular signal lamp was a round housing. Stacking support was provided by an external frame that came in 1, 2, 3 and 4 lamp configurations. Still, you have to give US&S a point for versatility since these units could also be arranged on a circular target signal in a 3 lamp configurations. Again note the Plain Jane construction which was common in the high labor cost/pre-CNC period.
Anyway, if anyone knows the actual model designations of these signals please let me know and I'll update the posts. Also, I assume that the design and market life of these signals probably went beyond the 80's on one side or the other, but that would make less of a compelling title.