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).
Test record for a speedometer, showing readings at various temperatures.
| Identifier | ExFiles\Box 59\2\ Scan028 | |
| Date | 3rd June 1929 | |
| X.4308. A.T. SPEEDOMETER TEST. Speedometer No. D999.720. "/50 Speedometer type 20HP From stock Other particulars 50.0 Temperature (°C) Miles per hour indicated at 600 R.P.M. exactly. Revs. per mile of drive for correct speed reading. 15.0 | 51.9 | 693 20.0 | 51.4 | 700 22.0 | 51.1 | 704 25.0 | 50.6 | 712 28.0 | 50.4 | 714 30.0 | 50.4 | 714 35.0 | 50.3 | 716 Miles per hour at 1200 R.P.M. 3.6.29. EFC. | ||