Vintage JT Hand held Pocket Watch Voltmeter In Its Original Box

This Vintage JT Hand held Pocket Watch Voltmeter In Its Original Box is a wonderful design.
In fairly good condition, there is some discolouration, loss of chrome, and surface scuffing / fraying commensurate with age and use. It has not been tested and I don't know whether or not it is working.

The blue cardboard box is intact with discolouration and a few tears / creasing. The box face is impressed with an impression of the voltmeter.

It has 2 ranges:
0 to 12 VDC
0 to 120 VDC

Approximate Size: 5.2 cm in diameter & 2 cm in depth.

It resembles the generic radio voltmeters made in France/Switzerland during the same time period. It seems likely that the same factory made ammeters/voltmeters for different companies and badged them under several names. The identity of the manufacturer J.T is unknown.

This piece of vintage technology would have been carried around in a pocket as a handy tool for the engineer to make a quick (but not necessarily accurate) measurement. It now makes an interesting display item for a vintage engineering tool collector, or a tactile desk ornament. 

NB: The images have been taken with and without flash hence the differences in colour.

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