[GreenKeys] M33 "O" (oh) vs "0" (zero)

[Jim Haynes]

One difference was when 1961 (approx.) ASCII was replaced by
1968 (approx.) ASCII.  The left arrow was replaced by an underline,
and the up arrow was replaced by something and another change or
two.  I was at UCSC at the time, and we had some computer languages
that made use of the characters that went away.  So even though our
order quantity was small we persuaded Teletype to make a compromise
type cylinder where the underline was somewhat arrow shaped
and the other changes were recognizable.