You seem well educated in this. Great information. I have a question for you (or any of our other smart people here)

What was the proceedure, when encoding, to correct a typographic error -- The operator ment to hit the letter "U" but instead hit the letter "I"

With the rotor advancing per key stroke there is no "backspace".

Would the operator encode the word "error" (or something to indicate an error was encoded) and then re code the word correctly and press on?

I imagine that the operator did not want to make too many errors, so this might slow down the speed of encoding