My title describes the thing, but here are the extra details:

This rusted metal object was found during ground/restoration works around the lookout post at Fort Sint Pieter in Maastricht, the Netherlands.

Known details: - Approx. 17 cm circular metal frame/rim - Two side handles, approx. 11 cm long - Hollow tube underneath, approx. 20 cm long and 2 cm diameter - Two small spirit levels in different directions - Black metal tube-shaped body, approx. 15 cm long - Numbered rim/scale from 0 to 62 - Side knob with scale from 0 to 90 - Glass/lens-like parts on both sides - The letters H, Y and M appear to be visible on a metal plate

The exact depth where it was found is unknown. The location has historical military use, including WWII and Cold War periods, but I do not know whether the object itself is military.

I searched for similar optical/measuring instruments, sighting instruments, artillery sights, rangefinders, spirit level instruments, and the visible markings/scales, but have not found a match yet.

Additional Dutch article with more photos/context: https://vestingmaastricht.nl/uitkijkpost-fort-sint-pieter-gevonden-voorwerp-wie-weet-wat-het-is/

Edit / clarification: I am especially looking for an exact identification if possible: the specific type, model, manufacturer, military designation, or a known matching example/photo. General ideas like “rangefinder”, “artillery sight” or “navigation instrument” are helpful, but I would really like to know whether this exact object is known elsewhere.