Megger safety ohmmeter, manufactured by Evershed & Vignoles Ltd., London. A portable insulation resistance tester designed to measure electrical insulation in wiring, cables, and electrical equipment. Operated by a hand-cranked generator, producing high test voltage to check insulation integrity in power installations and industrial systems. Instruments of this type were widely used by electricians and maintenance engineers for safety testing. Mid-20th century, c.1940s–1960s.
