This compass was produced by T.G.C. (The Gramophone Company - part of the EMI group.). On the underside of the compass are the serialnumber and a makers identification mark together with a broad arrow stamp.
Normally TG&C compasses were made by F.Barker &Son. The letter "B" was applied as a prefix to the serial numbers of all military compasses manufactured by F. Barker & Son. This compass hasn't. So it's rather special.