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).
Note comparing the weight of a Square engine to a Phoenix engine.
| Identifier | ExFiles\Box 91\1\ scan0505 | |
| Date | 19th May 1937 | |
| Square engine of the same capacity as the Phoenix would weigh 5% lighter (accessories excluded) or 25 lbs. (Phoenix without access. 500 lbs.) ROLLS-ROYCE, LTD PRINT ROOM MAY 19 1937 OSHS | ||