ID: 
2560
Maker's Name: 
Evershed & Vignoles
Where made: 
England
Dimensions: 
14 × 17.5 × 7 cm

Used to measure very high resistance such as insulation by measuring the small current that flows when a fairly high voltage is applied.

The instrument has three ranges:

1) Megohms with 500V applied

2) Ohms with 300 mV applied

3) Internal battery test

A transistorised inverter is powered by 6 AA cells.