A Galvanometer; but what was it for ?

This instrument is a galvanometer, a meter used for balancing or testing an external electrical circuit. In the days before absolute measurements were reliable the method used was to connect a known fixed resistance, a battery, and a variable resistance across the circuit to be measured, in what was known as a "bridge" configuration. By altering the value of the variable resistance the resistance of the external circuit could be calculated. A galvanometer, which is a centre-zero meter, often a moving coil type, was connected so that positive and negative current could be balanced out. At the point where the meter read zero the variable resistance setting was read. Often this resistance was in the form of a box carrying plug-in shorting elements such that a very accurate value could be read by adding up the resistors not being shorted out.

This meter is interesting in that the needle is not held in place by a hairspring but relies on reading centrally through gravity; that is when the case is resting in a vertical position. The top photo shows the meter lying on its back, hence the needle is askew.

The top is made from ebonite and is engraved with the words "INTy" and "QNTy". The "y" in both cases are superscripts. These abbreviations stand for "Intensity" and "Quantity", terms which were outmoded long before Victoria's reign was over. There is a small lever to the bottom right which has two positions, "1/5" and "F". Dial bezel, terminals and the carrying ring are all brass, the internal electrical fittings are copper and brass, and the case is a rough zinc casting.

The manufacturer is "WALTERS E.M.Co.LTD. LONDON"

Although knocked around a bit, the instrument appears to be in good order... but what was this model used for and when was it made?

I would hazard a guess that it was used to test detonator circuits, maybe in a coal mine?

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