A wartime Clinometer Sight, Mark IV, dated 1943, manufactured under contract in Canada and marked R.E.L. Canada (Research Enterprises Limited, based in Leaside, Ontario). This precision optical/mechanical device was employed with the Vickers Medium Machine Gun as well as various artillery pieces, enabling accurate calculation of elevation and depression in indirect fire roles. Constructed in brass with a brown protective finish, the instrument is fitted with a spirit level, degree markings for elevation and depression, and fine adjustment dials. Clearly stamped with its wartime markings: “1943 – C.O.S. 5908.A – R.E.L. CANADA – CLINOMETER SIGHT C. MK IV – 3178-C.” Canadian-made examples are scarcer than their British counterparts, reflecting Commonwealth wartime production efforts to supply Britain and Allied forces during the height of WWII.