ID: 
650
Maker's Name: 
AVO
Where made: 
England
Dimensions: 
14.5 × 9 × 3.5 cm

This is a mutimeter to measure Volts Amps and Ohms. The required function is chosen with a rotary switch. The meter is placed acroos a circuit to measure voltage, and in series to measure current. An internal battery in series with the meter permits the measurement of resistance.