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).
List of two Hasler revolution counters with their corresponding serial numbers.
| Identifier | ExFiles\Box 33\5\ Scan059 | |
| Date | 28th October 1924 | |
| X. 2675. EFC2/T28.10.24. X.2675. HASLER REVOLUTION COUNTERS. Hasler revolution counters belonging to this Dept. are as follows :- No. 5596 No. 2687. EFC. | ||