WW2 British Army Morse Indicator, morse-code trainer. 
Rotor-tutor  Self Instructor and Practice Board. 
 
Dimension- 14 x 13cm
 
FREE POSTAGE ON THIS ITEM.
 
Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called dots and dashes or dits and dahs. Morse code is named after Samuel Morse, an inventor of the telegraph.
 
source: https://en.wikipedia.org/wiki/Morse_code (citations removed).