Yours looks to be a nice example. Can't tell you much about them though. I got one a while back but it's missing a few small bits, and was purchased out of curiosity more than anything. I intend on getting it servicable enough one day to do a range test whilst mounted on modern production mount that sits in place of the sight ramp. (The original rifles had a special rear sight base with the mount integral on the side, requiring a small relief cut in the fore end- I think!)
More or less the first ACOG (an optic for general issue rather than snipers), but with long eye relief.
New production mount for the scope that requires no permanent alteration to the rifle is on the left.