The self-reducing tacheometer with base bar was made in 1957. It was designed for detailed measurement of lower precision in difficult and inaccessible terrains, trigonometric altimetry and measurement of distances, heights and directions for geographical, geological, agricultural and forestry purposes.

The instrument allows the measurement of horizontal directions, zenith distances and lengths. The special feature of the instrument is optical distance measurement. 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. At the coincidence of a double image, the position of the prism is read from the division. When this position is converted into the appropriate unit, it directly represents the horizontal distance to the point to be measured. Optical wedges are supplied which refract the beam for different angles. This determines the scale of the base and consequently the range and precision. The maximum range is 600 m and the precision ranges from 0.2% to 3%.

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