I was told we kept the mechanical encripters a long time. Because the keyboards of the electronic version emitted plain text and was suspect on security.
Of course in today’s world it is all micro-burst spread spectrum.
Every detail you wrote is accurate. The system as the Navy was using it for a backup in the late 1970’s had...at least six rotars, with 32 strands and 32 pin holes.
Took a couple of hours to do that ‘end of month’ set up...and then of course you would test it, and pray you did all the rotors and all the pin placements correct...or you had to break it down and start over.
Pain in the butt...but it worked.
And yes, the keyboard apparently did give off an electronic signature. We had some odd ‘techs’ checking that out...it wasn’t til several years later while watching the television ‘docudrama’ about the Walker spy ring I realized thats what they were doing there.
I was actually depicted in one brief scene of that tv movie, when a radiation leak was faked by one of our subs, so as to provide a trail to that spy ring. I was working the emergency circuits for the subs in the Atlantic, Med, that day.