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).
Blueprint showing a modification to a valve, with a larger size and steeper taper.
| Identifier | ExFiles\Box 151\2\ scan0082 | |
| Date | 20th July 1933 guessed | |
| Hs. {Lord Ernest Hives - Chair} 1071. .625 DIA .550 +2 110 350 DIA 437 DIA 30° MOD TO FX10839 HAVING LARGE VALVE AND STEEPER TAPER ON VALVE. | ||