Physical description

Course and Speed calculator used as a navigational aid by Air Force pilots to calculate aircraft relative groundspeed whilst allowing for wind speed and direction.

A similar example (MKIIA version) can be seen at the following Imperial War Museum web page:


Manufactured in the UK by E. R. Watts & Son.

Inscriptions & markings

Inscribed "COURSE & SPEED CALCULATOR MKII", "E.R.WATTS & Son No 757/35", "A.M. REF No 6B/119".