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 of a fractured spark plug.
| Identifier | ExFiles\Box 162\3\ img148 | |
| Date | 25th January 1939 guessed | |
| 6000, B, LG, PLB50N, S.A.C., MADE IN U.S.A., CHAMPION | ||