In the last picture the
Armstrong Whitford Whitley Navigator on the chart between the Dalton Computer and the Straight Edge is a Dalton Protractor. This very useful tool is not an invention in the 30's by an Ivy League whizz kid but a true British piece of kit invented whilst still a Captain by Vice-Admiral Sir Henry Percy Douglas KCB CMG FRGS FRAS AICE (1 November 1876 – 4 November 1939) a British naval officer who specialised in surveying and was Hydrographer of the Navy.