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).
A.T. speedometer test sheet recording readings at various temperatures.
| Identifier | ExFiles\Box 59\2\ Scan037 | |
| Date | 20th June 1930 | |
| X4308 X.4308. A.T. SPEEDOMETER TEST. Date 20. 6. 30. Speedometer No. C.561.740. 11/52 98.6 Speedometer Type 20 H.P. off 14G4 Other particulars Change of reading test after 10000 miles Temperature (°C) Miles per hour indicated at 600 R.P.M. exactly. Revs. per mile of drive for correct speed reading. 20.0 | 51.2 | 703 22.0 | 51.1 | 704 24.0 | 51.0 | 706 26.0 | 50.9 | 708 28.0 | 50.8 | 709 30.0 | 50.7 | 710 32.0 | 50.5 | 713 35.0 | 50.5 | 713 Miles per hour at 1200 R.P.M. 23.5.30. EPC. | ||