My original SSN card has "not valid for identification" printed on it. Originally, it was supposed to only be used for filing taxes. The first 3 digits identified the state you applied in, the second 2 digits identified the office (in that state) and 2 of the last 4 digits identified the filing cabinet.

Over the years, it ended up becoming the de facto federal identity number. It has no check digits, so you can make up any you want (I used to use a phone number of a major customer - only dropping 1 digit). I was a rebel/jerk/butthead back then. Now I just yell at clouds.

Long ago, I worked at a place that handled electronic prescriptions, lab results and insurance claims. There were huge numbers of incorrect SSNs which meant there were huge numbers of duplicates. Someone transposed 2 digits? Yep. Someone remembered their number incorrectly? Sure. Someone made one up? Like from a phone number? Oh noes! Before 911, trying to match someone with faulty ID numbers and messed up names was called "patient matching" and after 911 all the academics doing research into this stuff disappeared into large defense contractors or 3-letter-agencies trying to find more terrorists/bad guys.

For a good start in this area of research, I recommend this dissertation:

> Adaptive detection of approximately duplicate database records and the database integration approach to information discovery

> AE Monge - 1997

https://scholar.google.com/citations?view_op=view_citation&h...

> The most misused SSN of all time was [see link]. In 1938, wallet manufacturer the E. H. Ferree company in Lockport, New York decided to promote its product by showing how a Social Security card would fit into its wallets. A sample card, used for display purposes, was inserted in each wallet. Company Vice President and Treasurer Douglas Patterson thought it would be a clever idea to use the actual SSN of his secretary, Mrs. Hilda Schrader Whitcher.

> The wallet was sold by Woolworth stores and other department stores all over the country. Even though the card was only half the size of a real card, was printed all in red, and had the word "specimen" written across the face, many purchasers of the wallet adopted the SSN as their own. In the peak year of 1943, 5,755 people were using Hilda's number.

https://www.ssa.gov/history/ssn/misused.html

Most state agencies redact the SSN from public records. I want to say that they all do, but I work for a state and I see too many in all the wrong places.