My Dad carried this 15-2 in Vietnam. ser. K575824 My favorite revolver.
Great Caesar's Ghost, Bill!
Your picture of the USAF 15-2, serial number K558758, has non-relieved target stocks. Beautiful, although clearly not original to that revolver.
Every Model 15 ever issued to me in my two years in SE Asia had Magna stocks. I don't recall inspecting the frame on every one of them so that I can say whether they had U.S. or U.S.A.F. on them. That wasn't exactly a major concern of mine at the time!
I'm sure it was one or the other . . .