This is a heavy solid brass air-damped reproduction of a Mark III handheld British Prismatic Military Marching Compass. Approximate Size Length: 4 Inches / 10.2 cm Diameter: 2.4 Inches / 6.1 cm Thickness: 1.25 Inches / 3.2 cm This is a Reproduction Item, Not Sold As Antique. This Solid Brass Engineering Lensatic Compass is available in a polished brass finish. The compass card has the standard 0 - 360 degree scale, as well as the 0 - 64 Mil scale (one yard at 1,000 yards). The lid opens and the front prismatic sight folds over the compass to function as the front sight.  The prism has a magnifier to allow viewing the compass card and the object being sighted simultaneously. The height of the front prismatic sight can be adjusted to focus the compass card.  The lid has a scribed line in a glass window to serve as the rear sight, and the glass is protected by an exterior guard.  A brass bezel can be rotated and is marked off in 10-degree increments.  The bezel has detents so you can change the heading reference a known amount without looking at the compass.  A side adjustment varies the tension on the detent mechanism.  The outside diameter of the compass case is engraved with a compass rose for fast determination of rough direction