This prismatic fluid compass is smaller than his successors, the Mk 2 and the Mk 3.  It has the size of a Verner’s pattern compass, where the Mk2 was larger and the Mk3 larger still.  The patent numbers are British and registered to F. Barker & Son, and this compass was manufactured between 1926 and 1930.  In 1930 it was followed by the Mk2, and then in 1932 by the Mk3.

Contains Radium paint. (0.8 micro sievert/h)