Anyone know how to identify a Matte blue combat master with adjustable sights? It is a carbon steel gun with a serial number in the 21000 range (serial C21XXX), and it is marked Seattle, WA. It does not have "Mark IV" or any other identification (other than the Detonics 45 name) on the slide, and the slide isn't polished like a Mark IV. The box has "matte blue" written on the side.