Note that the left hand backsight has the full length No4 type screw, adjusting. I bet that was one of ours. We didn't differentiate at all. The backsight screw was the backsight screw to us and 400 still read 400 regardless!
Note that the left hand backsight has the full length No4 type screw, adjusting. I bet that was one of ours. We didn't differentiate at all. The backsight screw was the backsight screw to us and 400 still read 400 regardless!