A clinometer is used to accurately set the elevation of a field gun or heavy machine gun so that the shells follow the correct trajectory and land at the range required. Over the years there have been many different patterns of clinometer issued by the British Army, but by the time of the Second World War the Mk VI was used by many artillery units and production was to continue into the immediate post war period. The Mks IV and V were the examples used during the Great War and it would appear the Mk VI was developed between the wars, most likely as a way of reducing costs and speeding up production as this had been noted as a problem in World War I. The instrument itself is made of finely machined steel and is in the form known as a quadrant (other patterns that looked rather different were also available) The clinometer was issued in both wooden and leather cases, although my example has neither :

The clinometer could be rested on a field gun by a gunner to quickly read off the angle of elevation, before adjustments were made. The base of the clinometer has a heavy stand and an arrow showing in which direction to use the instrument:

The central arm pivots and can more up and down, the angle being read from the scale around the edge:

In order to use the inclinometer, the base was placed on the gun and the central arm moved up and down until the spirit level built into it was showing level, at this point the scale could be read to see the angle of the barrel. The spirit level itself is sadly broken on this example, but it can be seen that the frame surrounding the level has the clinometer’s designation and a year of manufacture- in this case 1953:

These instruments are beautifully made and were clearly very expensive when new, sadly they are worth very little on the collectors’ market as there are plenty of them around and of limited appeal to collectors.