This Clinometer designed by A.K.&S.Ltd dated 1916. The Clinometer was used for sighting long firing or a fixed line from a Vickers .303 inch Machine Gun. 
The leather case was made by T.French & Son Ltd, date 1918. Both Clinometer & case are broad arrow stamped.
The top of the Clinometer sight contains a spirit level. With each end, has a brass and steel winder that can depress or elevate the Clinometer from -20 degrees to +20 degrees.
The bass scale is graded in five degree units. Once this is attached to the Vickers, it allows it measure against the Clinometer to find the angle of elevation once the barrel is raised.
”This item was used by the British Army in both World Wars”