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).
Comparative table of test results for various magneto models.
| Identifier | ExFiles\Box 4\5\ 05-page155 | |
| Date | 24th June 1921 guessed | |
| 4C. A.{Mr Adams} Contd. Magneto. | (17) Contact breaker tripping speed (R.P.M.) | (18) Primary resistance (ohms). | (9) Secondary resistance (ohms). | (20) Secondary m.s. on 168 volts 50~ Hor. Vert. | (24) Remarks. --- | --- | --- | --- | --- | --- Watford. | - | .54 at 19°C. | 3319 at 19°C. | - | - | " | - | .535 at 18°C | 3057 at 18°C. | 15.5 | 9.4 | " | - | .51 at 14°C. | 2600 at 15°C. | 20.3 | 9.6 | " | - | .49 at 16°C. | 2840 at 17°C. | 20.1 | 11.2 | R.Bosch. | - | .73 at 15°C. | 2849 at 16°C. | 9.4 | 5.3 | U.S.A. Bosch. | - | .935 at 20°C. | 3166 at 21°C. | 8.4 | 6.7 | Low speed sparking characteristics taken before endurance test on which test magneti broke down on H.T. brush. U.S.A.Bosch. | -- | -- | -- | -- | -- | Dixie. | - | .68 at 16°C. | 3458 at 16°C. | 12.8 | 8.4 | Conner. | - | .51 at 18°C. | 2400 at 19°C. | 13.6 | 8.1 | B.T.H. | - | .76 at 14°C | 2690 at 16°C. | 22.4 | 16.3 | Gap had to be increased to obtain slow speed figures owing to distortion produced on endurance test. | ||