Re: 33ASR/33KSR keyboards...
Well, they DID have a backslash, you needed to look for it. Most of the time it was unlabeled.
If you have a model 33 teletype (or 35 for that matter), just press your friendly shift key and strike the 'L' key and it will magically appear. Other glyphs available are:
Shift 'K' - '['
Shift 'L' - '\'
Shift 'M' - ']'
Shift 'N' - '^' (usually an 'Up arrow').
Shift 'O' - '_' (usually a 'back arrow').
Shift 'P' - '@' (this one was usually on the key).
If you got stuck with a non-parity keyboard that had 'alt mode' and not a true escape key, the proper incantation was: Control/Shift/K.
We now return from the 60's/70's to your regularly scheduled program.