Special Features:

Titem has three calibrated scales: apds-t, m392 scale 0 to 7.31 mils: 0 to 2800 yds: hep-t, m39 (1.3 bias) scale 0 to 69.5 mils: 0 to 3200 yds: heat-t, m456scale 0 to 51.9 mils: 0 to 4400 yds; surface quality within circles shown after etching: inner zone (.787 dia)10-5: outer zone (1.575 dia) 20-10; all horizontal etched lines and spaces on hep and apds are centered on the 2 degree 15 minute draft line.Centers of dots to becoincident with lines defined by the ends of the horizontal lead lines

Properties:

An item, usually made of glass, having fine wires or hairs, or etched or printed fine lines on a surface, and placed in the focal plane of an optical instrument to establish a reference point to the axis for the purpose of aiming, measuring, ranging, and the like. Excludes lens, optical instrument.