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).
Calibration chart comparing Tachometer and Hasler rev counter readings for Hall's Car.
| Identifier | ExFiles\Box 90a\2\ Scan225 | |
| Date | 1st October 1934 guessed | |
| HALL'S CAR FILE Tach. Hasler. 500 455 1000 940 1500 1435 2000 1935 2500 2452 3000 2980 3500 3448 4000 3940 4500 4414 Rev. Counter. E.R. Hall - Shelsley. | ||