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).
Graph titled 'Low Compression' showing a relationship against revolutions per minute.
| Identifier | Morton\M22\ img080 | |
| Date | 5th May 1921 | |
| LOW COMPRESSION. Revs Per Min: 1500 1750 2000 2250 30 25 20 15 10 5 0 ROLLS-ROYCE, LTD. PRINT ROOM -5 MAY 1921 DERBY | ||