The Social Security Death Index (SSDI), or Death Master File (DMF) is an index of the deaths of US persons that have been notified to the US Social Security. It's available online at various places including [FamilySearch](https://familysearch.org/search/collection/1202535). It shows the social security number (SSN), age, and (for more recent data) the last place of residence of a person.

I understand that the primary use of the SSN on these records is to [apply for a copy of the person's social security card application form SS-5](http://www.legalgenealogist.com/blog/2013/05/31/ordering-the-ss-5/), which often reveals information about them (such as parents names). 

In addition, it's possible to find the place of issue of an SSN (issued before 2011). This is listed as "state" on the FamilySearch results. It can give clues as to where a person was (with many exceptions) when they first needed a Social Security card, such as when they first started working.

**However, are there any other uses for the SSN?** Are there any US public records, applicable to a deceased person, that use or include the SSN? For example, is there such a thing as a historical credit file that might show residential addresses over time? Are there historical voter records that include it? 

Are there open historical tax records? Is the SSN used in public military records, or in university alumni records? (Whether the number *should* have been used for such purposes is outside the scope of this question).

In other words, given the SSN of somebody who died possibly decades ago, are there any other records it could provide a key to?