The Model 4 Geodimeter, introduced in the fall of 1958, measured 12 inches square, weighed about 35 lbs (plus the 12-volt battery and inverter), and had a range of 50 feet to 3 miles. New, it cost less than $5,000. But for those surveyors worried about cost, AGA promised that the initial outlay was "easily returned by the savings gained in just a few projects' use." "System Bergstrand" refers to Erik Bergstrand, the Swedish physicist who developed the science on which the Geodimeter rests. The first two digits of the serial number may indicate that this instrument was made in 1959. The base is marked "X590314" while the power unit is "X590316."
Ref: AGA, Introducing the Model-4 Geodimeter.