6x15 optical tube for the observation triangle of the optical factory "FOS", mod. 1910

An original and extremely rare optical tube produced by Alexander Ginsberg's FOS (Optical Projectile Factory) in Warsaw in 1910. It was part of an artillery device designed to adjust the artillery fire of fortress artillery called the Artillery Triangle. The device was used to determine the correction for the lateral component, i.e. the correction for the amount of change in the direction of flight of the projectile per unit of time, and to adjust the firing range.
The devices were used in pairs, i.e. from different sides of the firing gun at a considerable distance from each other, but within visual visibility of each other, and were necessarily provided with telephone communication with the command post to transmit data after firing. The telescope consisted of a removable device assembly, had a special bracket for mounting on the triangle's sighting bar and a leather case. A special angle-measuring grid engraved on the glass was installed in the field of view of the eyepiece. Artillery triangles have been used in the Russian army for land and sea fortresses since the mid-80s of the 19th century. An extremely rare sample of the FOS factory's products on the antique market. It has also not been marked anywhere in museum collections yet. Guarantee of authenticity.