That document referred very clearly to ASCII (the 1967 variant), by "seven-bit code proposed by the International Standards Organization". There was no other character set that could be referred to by these words. Probably at the time when the document had been written it was not known yet that the number of the standard would be ISO 646.

The 1963 ASCII version was very different from the 1967 and later versions, it did not even have lowercase letters.

ASCII-1963 must be considered as a different character set from the later ASCII versions. It had a very limited adoption as a method for storing text in computers, because in the beginning only IBM System/360 had 8-bit bytes, while most other computers still had 6-bit bytes, and System/360 used a much more complete character set, EBCDIC, for storing text.

Thus ASCII-1963 was used in the beginning only for communication on serial lines, e.g. in terminals like Teletype Model 33, where it had the advantage of having more control characters than 6-bit character sets, even if it had only about the same set of printable characters. For storage, an ASCII-1963 string would have been converted to some 6-bit character set, because there was no need to store control characters and the number of printable characters was less than 64.

In most contexts references to "ASCII" should be understood as referring only to the 1967 and later versions, which were complete 7-bit character sets and which were adopted as both US and international standards.