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).
A spare W7Z engine unit and an obsolete 20/25 unit bored out to 25/30.
| Identifier | ExFiles\Box 27\3\ Scan011 | |
| Date | 13th January 1939 guessed | |
| Rm.{William Robotham - Chief Engineer} W7Z unit ex SG{Arthur F. Sidgreaves - MD}'s 25/30 in spare. Obsolete 20/25 unit bored out to 25/30. Pimkswol | ||