JMPO if they were to organize it any manner at all it would be the social security number. In the AF the 1st thing any spouse learns is their AD spouses social. Be married long enough like me, and when someone asks for your number you will need to think twice about what is your social security number because in the AF you live by the last 4 social of the AD member to do any kind of paperwork.
~ Can't tell you how many times I gave DHs for them to tell me it did not match....OOPS that's right you guys aren't military, you actually want mine.