This is how we find things out!!!!
This is how we keep issues alive until a proven conclusion is reached!
I guessed that the field was broken up into the subfields suggested by "xxyyzzz". The purported-to-be-Obama's middle sequence is 1125539. My son's number is lower than that but in the same ballpark. Yet they are on opposite parts of the country and Obama is twenty two years older. So there's a strangeness there.
I tried to check my own selective service number, but the on-line records only are available for those born on/after 1/1/1960.