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 a battery efficiency test.
| Identifier | ExFiles\Box 49\5\ Scan325 | |
| Date | 28th January 1922 guessed | |
| X.4288. Battery recived charged from Transport Dept. upon which efficiency test is to be carried out. Average amps = 9.85 40.6 amps Hrs TRADE MARK REGD. | ||