Apparently so, since you're looking at one. There were many M15's that didn't go to the USAF; that must be one of them, maybe it was Parkerized to try passing it off as a military-owned gun. The serial number range the M15's were within also included other K- frame models than M15's so the SN's aren't consecutive with any given model. To know the precise history of the gun, you'd need to have it lettered by SWHF.