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).
Note regarding an extra heavy valve spring.
| Identifier | ExFiles\Box 56\2\ Scan075 | |
| Date | 2nd May 1929 guessed | |
| E78071. Extra heavy valve spring | ||