MIL-S-48573 Sightunit, M64This specification covers one type of instrument known as Sight-unit: XM64E2 used with the Lightweight Company Mortar, 60MM XM224 \(See 6.1. Throughout this specification this instrument is referenced as "sightunit." This sightunit is composed of Telescope, Elbow: 11733780 and Mount, Telescope: 11741796. This sightunit has radioactively illum-inated scales, level vials and reticle.