See 70 years of ITC

Introduction of the ITC stereo trainer

A classroom with stereotrainers where students learned to interpret aerial photographs. Commercial instruments were very expensive, so their number was necessary limited. In order to meet training needs, the ITC developed its own much simpler stereotrainer.
The ITC stereotrainer was used in survey training around the globe. 
(Taken from "60 years of ITC", Nil Disco (2010), p50)