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).
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| Identifier | ExFiles\Box 168a\3\ img519 | |
| Date | 1st May 1950 guessed | |
| SEI Exposure Photometer | ||