The WK-20-8500 Observation Theodolite is designed for permanent facilities. Instead of a battery case, there is wiring that terminates in a twist-lock, male cap for the illumination system of the scales and reticule for night operation.
The WK-20-8500 has a 21-power main telescope and a wide 4-power finder telescope through one eyepiece. It has a full 360° horizontal circle and a 230° vertical circle, which permit sightings from zenith to 25° below the horizontal and the full traverse to the right or to the left. Both the vertical and the horizontal are equipped with positive drive gear, which can be quickly disengaged for hand movement.
Scales and reticle are illuminated for night reading. A mating connector is furnished for making a suitable length line cord for connecting to a 6.3V power source or the WK-22-4850 Pibal Timer . There is no magnetic compass and illumination is by 6 volt lamps.