The instrument shown below is called Modèle 26. It is marked Boussole topographique (i.e. Survey compass) but together with the abbreviation M.G. for Ministère de la Guerre, which meant it was issued to the armed forces by France's War Department.
The exact positioning of the divisions ring's inner black line in front of the needle was made possible by means of a prism attached to a swivelling fitting. The latter is stiffened on this item compared with the original design built by CRC. The compass's line of sight is represented by another black line drawn opposite to the knurled screw. The magnetic deviation could be adapted to a half degree. The corresponding scale features divisions from 20° West (occidt) to 5° East.
( Text by compassmuseum.com)