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\1\ img037 | |
| Date | 12th January 1939 guessed | |
| B LG S MADE IN F.L.B.O.A. ENGLAND PATENTED | ||