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).
Photograph showing a comparison of several engine poppet valves.
| Identifier | ExFiles\Box 97\5\ scan0159 | |
| Date | 14th November 1938 guessed | |
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