This is a Second World War, German Army Busch, liquid-damped, marching compass manufactured in 1934 or later. Liquid-damped compasses traditionally have a floating compass dial that turns instead of a moving needle supported over a fixed card – but occasionally there are exceptions.
Fluid acts to damp (a buffer, absorbing shock) for the horizontal circular oscillation of a compass card (a card with the points painted on it mounted directly under the needle, permitting navigators to read their direction from the top of the card) and allows the card to settle on north much faster than air-damped compasses.
There are many fluids that could be used, such as tap water, if the compass is very old and not likely to be used in the cold. Water is a valid damping fluid, but freezes near zero Celsius, which is the only reason other fluids are used. In the past a certain amount of glycerine was added to the water to prevent freezing.
The compass still works, with a working north point dial and minute increments. The dial still moves and the signal mirror is present, with the uniform suspension ring and outer cover case. The slide rule is also present on the bottom. The manufacture mark for Busch #68703 OR G8703 D.R.G.M. is stamped on the bottom.