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).
Cross-reference note regarding the 20/25 switchbox (general).
| Identifier | ExFiles\Box 56\4\ Scan148 | |
| Date | 31th December 1930 | |
| X.5730 31.12.30. For further matter relating to 20/25 switchbox (general) see X.6069. | ||