In the video Explorer 1 Preparation and Launch around the ten-minute mark the narrator says:
This particular Jupiter C, it’s serial number was 29, and that was coded in the missile. You see on the first stage just below the service structure the letters UE, those are the second, and ninth letters in the word Huntsville.
Is this known to be true? What about the pairs 7/8, 17/18 and 27/28, which would be indistinguishable (within a pair) and would all end in "L"?