From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Graph chart recording from a Megger electrical test showing amperes over time.
| Identifier | ExFiles\Box 54\1\ Scan213 | |
| Date | 19th July 1926 | |
| 19-7-26 154 S1. 75 a.h. 10/b. EVERSHED'S TRADE MARK "MEGGER" Average amperes = 6.25 Hours = 10.3 Ampere hours = 64.5 .640 1.80v X | ||