Text on this fluid compass is " Büchi, Bern Pat. Niedermann" . Niedermann patented this compasssystem in 1929. No degrees, but 6400 mils.
It shows a hinged mirror tilted by 45 degrees downwards, allowing a look at the compass rose from below. This system was also used ten years later by RECTA on its matchbox-style compass and after WW II by the German WILKIE.
The compass has a double inclination scale at both sides of the bakelite element:
0-110% (positive and negative) How to read it, I don't know.