Plastic processing specialty store Inoue style triangular ruler style nautical [Inoue Seisakusho] (Inoue ruler)

A triangular ruler used on nautical charts, etc., with scales such as elevation scale, distance scale, altimeter scale, eye height scale, etc., and azimuth lines. This item is from Inoue Seisakusho, a plastic processing specialist located in downtown Tokyo. Where do you usually sell it? We are selling rare (°д°) useful products!