Used on US 81mm and 60mm Mortars....
M4 collimator sight as depicted in FM 23-90. This sight was also used on the M2 60mm mortar. By laying the sight on aiming stakes, the mortar squad could fire indirect missions. The open sight allowed the squad to fire direct lay missions.....................BILL
"As long as there are brave men and warriors the halls of Valhalla will never be silent or empty"
In memory of my father William T. Grist December 26, 1920--September 10, 2009..
901st. Ordnance H.A.M. North Africa, Italy, Southern France....ETO
Also in memory of my mother Jane Kidd Grist Feb. 22, 1920-- September 27, 2009... WWll War bride May 1942...