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).
Performance comparison table for various dynamos.
| Identifier | ExFiles\Box 60\1\ Scan200 | |
| Date | 1st April 1927 | |
| (0%) 40.O N.B. DYNAMOS. PERFORMANCE COMPARISON OF DYNAMOS (On routine procedure of 1.4.27). Dynamo. | (8) Speed for 10V. 14V. 17V. | (9) Speed for 0 amperes at 12.4 V.{VIENNA} | Peak. Speed. Amperes. | 2500 RPM. amperes. | Remarks re commutation. | Remarks re silence. -- | -- | -- | -- | -- | -- | -- H.O.1 | | | | | O.K. | O.K. 2. NB.HO. | | | | | O.K. | O.K. 3. NB.HO. | | | | | O.K. | O.K. 4. NB.HO | | P II Type. | | | O.K. | O.K. 18. HO.SS.{S. Smith} | | | | | O.K. | O.K. | ||