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).
Photographic series documenting pattern changes at different numerical intervals, possibly RPMs.
| Identifier | ExFiles\Box 137\4\ scan0151 | |
| Date | 24th December 1930 guessed | |
| NOV 1 500 1100 2600 3100 4500 | ||