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).
Stating that 7-ringed pistons with skirts are superseded by 5-ring pistons and no further experimental work is needed.
| Identifier | Morton\M11\ img057 | |
| Date | 11th April 1918 | |
| EFC81/T11.4.18. 233 X. 2369B - 7 RINGED PISTONS WITH SKIRT These chassis pistons may be considered superceded by the 5 ring pistons and no further experimental work will be required. EFC. R.R. 2355 (200 T) (S.D. 408. 26-4-17.) Bm. 2/156/1 | ||