0083 is just the Federal Civil Service Occupational code. When I was in aircraft maintenance, my pay grade was a WG 13, but my specialty code was 2612.
Most Air Force installations used to have rent a cops to augment the active SP force. With the budget cuts, the AF has found that they can hire Federal DoD cops and get funding through Homeland Defense. All they are really doing is shuffling the money from one pot to another, but I guess it looks good to the bean counters.
Make sure your brother is getting credit for his time in the Corps, it helps for vacation days as well as counts towards retirement if he "buys back" his time.