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 resistance plug and a rheostat dial divided into degrees.
| Identifier | ExFiles\Box 175\4\ img131 | |
| Date | 1st May 1931 guessed | |
| 80 100 100 120 Resistance Plug Rheo Dial Divided into Deg. and 20ths of a Deg. | ||