Day 287/17 .Stereoscopic Mapping

A visit to Hughenden Manor today, the historic home of Benjamin Disraeli, the UK Prime Minister 3 x over and the UK's first and only Jewish born Prime Minister.
However what, in many ways, was more interesting was the use of the manor house in WWII. The house was seconded by the War Ministry and was used throughout the war to produce bombing maps for Bomber Command. This is a stereoscopic viewer with Photo Reconnaisance photographs that were used to manually produce the maps.
Almost certainly the Germans never discovered the use of the house, or it would not be there today.
The extra picture is of the house itself.