Ayrton and Perry's fixed coil moving needle non-commutator ammeter Ayrton and Perry ammeter, about 1880 1875-1884
5KV Ionisation Tester type 732 by Airmec Laboratories Ltd., High Wycombe, Bucks, serial no. 1639, c. 1980 5KV Ionisation Tester type 732 by Airmec Laboratories Ltd. 1971-1990
Precision ratio comparison bridge type VLF51A, by Rosemount Engineering Company Limited, Bognor Regis, Sussex, England, c.1980, with terminal unit model CSU A1. Precision ratio comparison bridge type VLF51A 1976-1985