Winkelmesser W.M.35 German Artillery & Mortar Level

Original German artillery and mortar winkelmesser W.M.35 in the original box. Missing the key. There is always a small flat unpainted area on nearly every piece of German artillery near the breach, that is where this would be placed and clamped down. This would allow you to calibrate the mounting of the sight block. It is in decent condition except for the bubble level, which is smashed.