Having been born in the late Pleistocene, I nevertheless still have my original Social Security Card, which states clearly at the bottom:

"Not to be used for identification".

Quaint as it may seem today, many back then did not trust the government idea of "helping everyone with retirement" by assigning all of the tax cattle a unique number which, although certainly not tattooed on one's arm, would nevertheless stay with each bovine for life.

Well, we all know how that worked out, eh?