1903 in magazine article explaining how sighting a rifle works (American Rifleman, June 1942)
(click for bigger)
https://www.milsurps.com/images/impo...ar194210-1.jpg https://www.milsurps.com/images/impo...ar194209-1.jpg https://www.milsurps.com/images/impo...ar194208-1.jpg
From this issue:
https://www.milsurps.com/images/impo...AR194201-1.jpg