[akdavis]

This isn't a real gunsight for macchi , Francesco .
If you see the picture , the R gunsight is PAINT on gunsight glass , this is why if you have a gunsight lamp broken , you can collide A=(iron sight) whit R=( paint sight on sight glass ) and you can sight .
You have a real San giorgio sight here viewtopic.php?t=22015
Ciao.

That certainly makes more sense considering the drawings.