I checked with the Computer History Museum about the 1620. According to Dave Babcock, IBM 1620 Restoration Team Lead at the CHM:
The 1620 console typewriter actually had a "zha" character typebar that it would use for unknown characters. The only overprinting that the typewriter would do was a "flag" mark [an "overscore" rather than an "underscore"] and a center-hyphen [used for characters with bad parity]. For both of these, it would first print the special character [flag or center-hyphen] without advancing the carriage, then print the other digit or alpha character. And yes, it was possible to get a "bad parity unknown character" which would print the center-hyphen and zha. The typewriter was not capable of backspacing to do any other overprinting. With the Wheelwriter-based console typewriter that we're using for the IBM 1620 Jr. we will be doing some real print-backspace-print overprinting to approximate some of the special characters, like zha. Ken Shirriff (the other Ken) On Mon, Sep 25, 2017 at 9:48 PM, Leo Broukhis via Unicode < [email protected]> wrote: > Wikipedia (https://en.wikipedia.org/wiki/IBM_1620#Invalid_character) > describes the "invalid character" symbol (see attachment) as a Cyrillic Ж > which it obviously is not. > > But what is it? Does it deserve encoding, or is it a glyph variation of an > existing codepoint? > > The question is somewhat prompted by > > 2BFF 1 HELLSCHREIBER PAUSE SYMBOL > > in the pipeline, although I learned about both earlier today within a few > minutes of one another. > > Thanks, > Leo > >
