The Micro sight is an add-on to what appears to be an original target sighted gun. I see the remnant of the factory rear sight, so I'm curious as to what's under the Micro.
Also, the stocks are much later than the gun...
*Edit:* The serial number you give is much too low for a 3rd model. What serial number is in the ejector rod shroud? The star on the butt indicates factory service of some sort, but it's doubtful they would have added the Micro sight.
Mark