Nice! I've heard about fixed four ways having blank doors. Looks like it's essentially a metal lens that bolts on where the visors normally get bolted on? Looks like the signal could easily be converted to a four-way by taking the blanks out, adding relfector/socket assemblies, and inserted lenses and visors. Good if a three-way intersection gets a road added to make it a four-way. Back then it probably would have been cheaper to do that rather than take down everything and install an entirely new signal set-up like most places do now. We've become such a wasteful country.

Yes, that is correct. Aside from Ruleta, other manufacturers, such as Eagle and Crouse-Hinds, offered blank doors for fixed four-way models.