IBM 1620 invalid character symbol

Leo Broukhis via Unicode unicode at
Tue Sep 26 01:34:34 CDT 2017

The glyph there looks more like U+1D219 Greek vocal notation symbol-51:
than a Ж.

If it was implemented as an overprint, either )^H|^H( or \^H|^H/ and was
intended to signify an invalid character
(for example, in the text part of core dumps, where a period is used by
hexdump -C), then there would not be a physical key to generate it.

On Mon, Sep 25, 2017 at 10:48 PM, Ken Whistler via Unicode <
unicode at> wrote:

> The 1620 manual accessed from the Wiki page shows the same information but
> with a different glyph (which looks more like the capital zhe, and is
> presumably the source of the glyph cited in the Wiki page itself). See:
> U_Model_1_Jul65.pdf
> p. 52 of the document (56/99 of the pdf).
> So there was some significant glyph variation in the 1620 documentation.
> My guess is that the invalid character tofu was implemented as an overprint
> symbol on the 1620 console typewriter (since the overlines and the
> strikethroughs clearly were). The whole system was basically using only a
> 50-character character set. But to verify exactly what was going on,
> somebody would presumably have to examine the physical keys of a 1620
> console typewriter to see what they could generate on paper.
> I'm guessing the Computer History Museum (
> ) would have one sitting around.
> --Ken
> On 9/25/2017 9:48 PM, Leo Broukhis via Unicode wrote:
>> Wikipedia (
>> 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?
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