Originally Posted by
Trakhak
That statement is off-topic, of course, but: the "Not For Identification" wording was more likely a legal disclaimer intended to absolve the Federal government of responsibility if you found yourself defrauded as a result of providing your SSN to a crook as a means of identification.
The disclaimer was removed from the card (in 1972, I just read; it had first appeared there in 1946) because an overwhelming number of non-governmental businesses and agencies had come to use it as a de facto means of identification over the years.