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).
Table comparing total mileage against carbon percentage for six designated items.
| Identifier | ExFiles\Box 97\5\ scan0211 | |
| Date | 11th May 1939 guessed | |
| (2). Designation. | Total Mileage. | Carbon %. ------------------------------------------ A | 11,543 | 80. B | 17,928 | 75. C | 22,337 | 60. D | 23,765 | 80. E | 27,211 | 60. F | 31,800 | 66. Hl./BPS. | ||