This after its first introduction became the primary test equipment for all Electrical and Radio engineers. It was by far the best instrument of its kind in the UK from 1923 to at least the 1960s.
Because it was easily portable it allowed measurements to be made in places away from the laboratory with an accuracy that became the norm for all engineers but was adopted in research facilities for every day work because of its compact size and range of facilities.
Prior to this instrument each of its functions required a separate and complex peice of equipment which was certainly not suited to work away from the laboratory.
In short it set a new standard that controlled the many and varied modern devices that followed in the 1970's and later. Many engineers me included still have one and still make use of it.
It is my belief that these Multi meters played large part in our technological success simply by being accurate and dependable in any environment. I can guarantee that all of the enginneers working on Radar in WW2 would have depended on it to set up many features of the system
The engineers that followed would all have used the AVO in its many versions that followed.