“The last four were simply random”
When I got my SS card, in the 50’s, my friend and I applied together and were given our cards. Her number is exactly the same as mine except the last four...mine was one number below hers....example, 1587 and 1588....
That is interesting.
I probably could have chosen a better word than random.
What I mean is the last four digits have no particular meaning. The others do.