Graph plotting a curve with an x-axis labelled B.D.C. and numerical increments.
| Identifier | ExFiles\Box 179\2\ img239 | |
| Date | 12th February 1932 guessed | |
| (SEE RINGS) 500 520 540 B.D.C. 560 580 600 620 | ||
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).