IBM 1620 invalid character symbol

Ken Whistler via Unicode unicode at
Tue Sep 26 00:48:26 CDT 2017

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:

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.


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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