Photograph of a disassembled spark plug, labelled 'A'.
| Identifier | ExFiles\Box 162\3\ img147 | |
| Date | 23th January 1939 guessed | |
| A | ||
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).