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 further information for 20/25 Horns (general).
| Identifier | ExFiles\Box 45\3\ Scan261 | |
| Date | 31th December 1930 | |
| X.4078 31.12.30. For further matter relating to 20/25 Horns (general) see X.6077. | ||