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 graph comparing the horsepower (HP) curves of various cars.
| Identifier | Morton\M4.2\ img026 | |
| Date | 1st January 1923 guessed | |
| HORS 30 20 10 0 500 750 MARMON CAR. - H.P. CURVE. BUICK CAR. - H.P. CURVE. HUMBER CAR. - H.P. CURVE. DODGE CAR. - H.P. CURVE. HUP CAR. - H.P. CURVE. | ||