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 of an electrical test measuring ampere-hour performance over time.
| Identifier | ExFiles\Box 52\4\ Scan061 | |
| Date | 28th June 1929 | |
| 28-6-29 221 Ediswan XSB 557-1-2 90ah 92ah Average amperes = 6.43 Hours = 11.0 Ampere hours = 70.7 .769 1.80w TRADE MARK 'RECORD' | ||