I have to bring a few things into question in this thread. Not saying they aren't true but definitely have some questions:
1) The T-Bolts being installed in '53. If that were the case, then they should have been jailbars yet I never ran across a jailbar unit in STL at any time.
2) More as a point of clarification: the 612s did not predate the Whelens. Rather, they were added later as gap fillers or replacements for malfunctioning units. The 612s all broke down and were replaced before the 2910s went in, save one unit in Ballwin (not listed earlier in the thread)::
https://www.google.com/maps/@38.5884864 ... 328!8i1664
3) Are we sure about the Allertronics? I've never seen any record of those. Both your locations have 4000s with 864 cabinets on StreetView imagery that predates the 2910s...which means if they were there they were gone within a matter of a few years. But as long as we've discussed St. Louis around here (and its been a long time) Allertronics have never once come up. Especially because the county installed several yellow painted 4000s in the early 90s to expand the system.