USAF Hummers have the same camo and stencil markings as the ones used by the Army. Standard markings of "USAF" (or US Air Force) with the registration number below it, i.e. 86K1234, would normaly be on edge of each side of the hood above the wheel wells.
Vehicles assigned to Security Forces Squadrons (or Security Police as it was in my day) might have "Security Forces" above the join line between the roof and chassis in the area above the rear tires.
Based on my experience, markings on the front and rear of the vehicle were inconsistant, some had them and some didn't. If one did, it was