I am sure the alloy sights were for the early models and in the 80s they changed over to the plastic ones. In my old Gamo parts book the front sight (as in my pics - part ref no 3384) is common to 15 of the 17 models listed (one didn't have open sights and the other had interchangeable ring elements). I seem to remember that alloy and plastic were interchangeable, but the memory isn't what I think it was?! Confirmation would be good. I am 90% sure it would fit.
The diameter of the barrel that the sight fits onto is 12mm, what is yours?