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 showing the results of an electrical test with calculated values.
| Identifier | ExFiles\Box 38\5\ Scan368 | |
| Date | 28th March 1923 | |
| X 3398 P & R B.D.T. 11/1 28-3-23 REGD TRADE MARK Amps per Div = .294 Average amperes = 9.85 Ampere hours = 45.90 Ohms in circuit = 1.17 | ||