Torpedo directors were used to calculate the moment of release of the torpedo from the coastal motor boat by sighting on the target and ensuring the boat and therefore torpedo were lined up with the target. The torpedo was released by being jettisoned backwards from the boat. The boat then had to bank hard to the left or right before the torpedo's motor was engaged. This particular design was to be used on coastal motor boat nos. 781 to 792.
This director was used on coastal motor boat No.4 when Lieutenant Beckett D.S.O. lead the first attack on Zeebrugge and fired the first torpedo from these craft in action on 6 April 1917. It was also used by Lieutenant Agar V.C. when he, with the same boat, attacked and sunk the Oleg at Kronstadt on June 17th 1919. It was presented to Miss Blanche Thornycroft in recognition of her work in carrying out the tank experiments of the models of the boats.
