If the information you found is from the typewriterdatabase, that is the information I recently shared.

I thought it might be a standard alternate type connector rather than a "proprietary designed" which IBM seems to love so much.
I can see why it would require the key. You wouldn't want someone plugging a 10 Base-T modular connector into the back of the IBM 85/95 Electronic Typewriter, or the 6731. Who knows what might happen.... Bzzzzzz *POOF!*
