The letter itself seems real, and the response is requested to a verified location :
Social Security Office, 1200 Reverend Abraham Woods Jr Blvd N, Birmingham, Alabama, 35285 United States

below is a rough description of what i consider suspicious CONTENT :

- claim that records need updating regarding a non-existent pension
- without citing a source, they purport a small monthly pension has been received for ~2 decades
- letter did not name which employer\source this non-existent pension came from, much less provide supporting documents
- they do not mention existence of any tax-related pension documents for the entire period (1099, 1040, etc...)
- cited pension date not coincident or correlated with any year of retirement-related event

oig\ssa are requesting the following from recipient :
- Open ended permission to collect data from all former employers
- Official contemporary summaries of pension payment from all former employers via photocopies

perhaps the SS# has been used for pension fraud? certainly a lose-lose scenario for the recipient.

i will be replying pension does not exist, but not complying. letter will indicate suspicious phishing\fraud has been reported to aarp, postal service, and state agencies.

again, the fact elderly are being targeted, will not understand the content, and potentially penalized if not responding should motivate anyone (dem\gop) angry.