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).
Diagram of an inverted 25 HP crankcase top half, showing an indicator clock on the centre main bearing.
| Identifier | WestWitteringFiles\V\December1930-February1931\ Scan158 | |
| Date | 20th January 1931 guessed | |
| SUPPORT INDICATOR CLOCK ON CENTRE MAIN BEARING. SUPPORT. CRANKCASE 25 H.P. (INVERTED TOP HALF) | ||