The black square marching compass was introduced in the Second World War as an alternative to the more expensive prismatic compass that had been in use since the First World War. This compass was made of Bakelite and when folded was a distinctive square shape with a small brass loop sitting over the main body of the compass:This brass loop was to slot your thumb through to hold the compass steady whilst a bearing was taken:The compass opened up into two parts, one was a silvered panel with a slot cut through it to look down when taking a bearing, whilst the other half had the compass itself:The dial of the compass sat around the luminescent needle and could be rotated to take a bearing:The following instructions were given for using the magnetic marching compass:
A: To march on a given bearing by day or night:
Rotate ring until given bearing is over the luminous arrow. Hold compass level and move it so as to keep the luminous needle tip between the two dots on the ring. March along the luminous line on the lid.
B: To read the bearing of a given object:
Hold the compass level and aim the centre line of the lid at the object, tilting the lid as required. Allow the needle to come to rest. Rotate the ring until the luminous needle tip lies between the two dots on the ring. Read the required bearing off the ring at the luminous arrow directly, or by the reflection from the mirror in the lid.
The compass could be used for night marching, similar to the process indicated in the pre-war Army’s Map reading manual for use with the prismatic type of compass:
Marching on a Compass Bearing.- The guide must know the bearing on which he wishes to march. He then observes some object which has the required bearing and marches towards it.
In the Service Prismatic Compass the magnetic north is marked by a broad luminous arrow-head. The glass cover is turned until the setting-vane on its rim, corresponding to the luminous direction mark on its glass, points to the required magnetic bearing as shown on the external ring; the cover is then clamped at this bearing. The box is now held so that the direction mark is superimposed on the arrowhead, in which position the line of the luminous patches in the lid, fully extended, indicates the line of advance.
Like many marching compasses, this example was made by ‘The Gramophone Company’ and their initials T G Co Ltd are marked on the rear together with a /|\ mark and the compass’ designation:T.G. Co. Ltd. was the abbreviation used by The Gramophone Company. This firm merged with its subsidiary His Master’s Voice (2/3) and with Columbia Graphophone Co. (1/3) in 1931 to become EMI (Electric& Musical Industries) who continued to use “The Gramophone Co.” trademark for various items, changing it for the War contracts to just T.G. Co. Ltd.
In reality, F. Barker& Son apparently built these compasses since they all carry the B prefix to the serial number.
T. G. Co. disappeared as soon as WW2 finished. This company name was probably used to keep secret the manufacturer’s real identity.
The letter ‘B’ in the serial number means that this compass was in reality produced by F. BARKER & Son.
Although a stop gap wartime design, the marching compass was well regarded as it was easier to use than the prismatic type and it continued in service into the post war era alongside the earlier and more sophisticated design for many years to come.