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).
Letter from Wellworthy Piston Rings Ltd. regarding Brinell hardness testing specifications.
| Identifier | ExFiles\Box 115\5\ scan0170 | |
| Date | 15th November 1938 guessed | |
| EXTRACT AERO COPY 1. results, that is whether it should be by Brinell or any other machine, and whether it should be by 5 mm. diameter ball or 10 mm. Yours faithfully, For WELLWORTHY PISTON RINGS LTD., Technical Manager. | ||