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).
List of ratios of field resistance to armature resistance for various starter motors.
| Identifier | ExFiles\Box 61b\3\ scan0086 | |
| Date | 15th December 1920 | |
| X543 6027 15.12.20. X.543 - RATIOS OF FIELD RESISTANCE TO ARMATURE RESISTANCE OF STARTER MOTORS. X.3174. C+A.V. .453 Lucas. .333 Bijur. A 21 .75 Bosch. .316 R.R.45A 1.79 R.R.45B. .731 Bijur 1AD. .82 Bosch U.S.A. .271 EFC. | ||