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).
Blueprint of a circular component with 26 equally spaced teeth.
| Identifier | ExFiles\Box 179\3\ img121 | |
| Date | 29th February 1932 guessed | |
| 1.890" 20" DIA 26 TEETH EQUALLY SPACED 5/16 WIDE UNDERCUT | ||