That C train which was used during the 1962 water main break terminated at 34th St.-6th Ave. I'm sure it seemed a bit odd to have a train marked as a C running via 6th Ave. and another train marked as a DD running via 8th Ave. Emergencies will do that. At least the R-1/9s had those signs available. BTW, I set my signbox for that unique C train: Concourse-Bedford Park and 34th St.
If I'm not mistaken, almost every letter of the alphabet was planned for the entire IND, Phase One and Phase Two routes combined.
I am pleased to report that someone finally made the New York connection with my license plates. This gentleman first said, "That must be the IND," then referenced Duke Ellington's Take the A train. He was a graduate of Columbia. I congratulated him for being the first person to identify my plates.
P. S. For those of you who didn't know, Dick O'Neill passed away in November. He played Frank Corrall in the original Pelham 1-2-3. My favorite line of his was, "Oh, nothing: a train is down, its radio's dead, the power's off, and it's dumped its load. Aside from that, everything's ginger peachy."