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).
Chart recording from a Megger instrument showing a battery test.
| Identifier | ExFiles\Box 38\5\ Scan288 | |
| Date | 6th December 1922 guessed | |
| X 3398 P+R BATTERY B.D. 11-2 amperes per div = 2.89 average amperes = 9.89 hrs per hour = 4.69 REGD. TRADE MARK "MEGGER" | ||