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 of engine unit weights in pounds (LBS) for various models.
| Identifier | ExFiles\Box 88\3\ scan0207 | |
| Date | 26th August 1936 guessed | |
| X258 ENGINE UNIT WEIGHTS, LBS. CHINA. PEREGRINE. J.III. 40/50 Engine. 565 417 480 871 Gearbox. 115 110 115 201 + TOTAL. 680 527 595 1072 40/50 Crank 100 lbs. SpectreCodename for Phantom III Crank 70 lbs. + Clutch pit included | ||