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 results for A.T. Speedometer No. 12800, showing reading vs actual speed and error.
| Identifier | ExFiles\Box 50\4\ Scan069 | |
| Date | 15th September 1924 | |
| X. 4308 Hs {Lord Ernest Hives - Chair} /Rm {William Robotham - Chief Engineer} /LG15.9.24 A.T. SPEEDOMETER. NO.12800. 690 r.p.m. mark. Fitted to 49-GB car. Reads. Actual. 20 17 30 25.7 40 34 50 42.5 60 51.5 Average error 15% fast. Rm. {William Robotham - Chief Engineer} | ||