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 showing the performance of two magnetic speedometers, charting the drop in M.P.H. reading against a rise in temperature.
| Identifier | WestWitteringFiles\W\May1931-August1931\ Scan067 | |
| Date | 19th June 1931 guessed | |
| M.P.H. READING 46 44 42 40 15 20 25 30 35 TEMP. DEGREES C. MAGNETIC TYPE SPEEDOMETERS CURVES SHEWING PERCENTAGE DROP IN M.P.H. READING WITH RISE IN TEMPERATURE WATFORD A.T. | ||