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).
Calibration data for a Record Mark I.A. Revolution Indicator, showing instrument errors at various RPMs.
| Identifier | ExFiles\Box 165\4\ img082 | |
| Date | 20th August 1930 | |
| X 1350 Calibration of Record Mark I.A. Revolution Indicator 20.8.30. Indicator Starboard No.15. Generator No.49. True R.P.M. | Instrument Errors, R.P.M. 600 | +5 700 | +5 800 | +5 900 | 0 1000 | -5 1100 | 0 1200 | 0 1300 | +5 1400 | +10 1500 | +10 1600 | +15 1700 | +15 1800 | +20 1900 | +20 2000 | +25 2100 | +20 2200 | +25 2300 | +25 2400 | +10 2500 | +5 2600 | -10 | ||