A precision optical surveying instrument of the Imperial Japanese Army, used for laying out permanent gun sites, airfields, and military installations — measuring precise horizontal and vertical angles for triangulation of defined targets and positions. Manufactured by Nihon Keiki Seizo Kabushiki Kaisha (Japan Instrument Mfg. Co.), dated Showa 18 Year 2 Month = February 1943. Serial number 53612 appears on both the instrument and the case tag. The instrument features a large red filter disc, precision optics, and fine adjustment mechanisms. Included: original metal lamp storage box with 6 original spare bulbs still in place, color filter glass, eyepiece, tools. The hardwood case has original metal edging, functioning latches, and a complete parts inventory plate inside the lid. An exceptional, largely complete WWII Japanese precision optical set.