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).
Check of the revolutions per mile for a 20 HP A.T. Speedometer.
| Identifier | ExFiles\Box 50\4\ Scan335 | |
| Date | 29th November 1929 | |
| X4308. 29/11/29. CHECK OF REVOLUTIONS PER MILE OF SPEEDOMETER. Speedometer :- 20 H.P. A.T. Speedometer No D 500. 720. 1/50 Date :- 29-11-29 Mile reading | Counter reading Observed at finish. | 00293 | 60740 Observed at start. | 00011 | 10000 Difference | 00282 | 50740 Counter revs. per mile | 180 Instrument revs. per mile | 720 28.10.29. | ||