Each compass has its original "mother of pearl" (no longer available on modern compasses because of conservation reasons) compass card which was hand engraved by ladies on a Taylor Hobson engraving machine. On the underside of the compass are ministry store reference numbers and a makers identification mark together with a broad arrow stamp.
This compass contains Radium paint. (5.5 micro sievert/h)!!!!!!!
A few British manufacturers names are:
TG+Co =The Gramophone Company - part of the EMI group., FB+Sons =Francis Barker, W F Stanley, GEC= General Electric Company