Diagram of a Pibal Theodolite
This is a illustration depicting David White 6061, 47 and early Warren-Knight models 47, 474 and 84 etc. Pibal Theodolites. A few units were also produced in the 1940's by Seiler Instruments under contract. The illustration and units mentioned above differ slightly from the current Warren-Knight production units in the style of the battery case. See the Pibal Models pages located on this site for for information on the variants of theodolites that are similar to this one as well as some interesting others.
Note that Warren Knight also makes a digital unit that looks quite a bit different than this one. Other digital theodolites as well as currently marketed balloon theodolites are featured on the Manufacturer's Pages on this site.
There are at least three prism types used in balloon theodolite optical paths, and a radically different optical path utilized in a marine theodolite.
