There were changes in 1965 and the 1967 version is considered the official one. Companies who adopted ASCII before that, like Xerox and DEC, had a left arrow in

There were changes in 1965 and the 1967 version is considered the official one. Companies who adopted ASCII before that, like Xerox and DEC, had a left arrow instead of "_" and up arrow instead of "^" in their equipment. When Smalltalk-78's internal character set was replaced by ASCII in Smalltalk-80, it was the 1963 ASCII that they adopted since that is what they knew at Xerox. Though the goal was to be friendly to the rest of the world, the fact that almost everyone else saw their assignments as underscore causes problems to this day. So it is possible that 1964 was too early for IBM to embrace ASCII. But to be fair, the 1963 x 1967 ASCII problems are trivial compared to any ASCII x EBCDIC.