Photograph of a broken spark plug with the threaded base detached.
| Identifier | ExFiles\Box 162\1\ img036 | |
| Date | 23th January 1939 guessed | |
| GS 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).