The self-reducing tacheometer with base bar was made in 1960. The instrument dates back to a period when people were frantically searching for a way to improve the precision of optical distance measurement. The instrument allows the measurement of horizontal directions, zenith distances and lengths. A special feature is the optical measuring of distances. The parallactic triangle with a fixed parallactic angle and a variable base at the station point is rectangular. The prism, which ensures a constant angle, is moved along the metal guide by means of a division. In the eyepiece, we observe a double image of the target point - one is direct and the other is provided by a moving prism. The prism is moved until the two images coincide. The position of the prism is read from the division, and, when converted into the appropriate unit, directly represents the horizontal distance to the point to be measured. The precision of the distance measurements is 0.06% or 6 cm per 100 m.

The instrument is in the same condition as when it was originally taken out of service, almost like new.