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).
Comparison table of 20 HP Dynamo Brushes from manufacturers Morganite and Le Carbone.
| Identifier | ExFiles\Box 50\5\ Scan200 | |
| Date | 17th July 1923 guessed | |
| X. 4333. X.4333 - 20 H.P. DYNAMO BRUSHES Quality. Morganite. Le Carbone. Hard graphitic E.G.2. = Z Sp.{Mr Spinney}res. .0012 = nearly EG30 with with alternative of EG60 for control brush. Softer E.G.O. graphitic. Sp.{Mr Spinney} res. .0006 Copper graphitic C.M.5 = CG2 Sp.{Mr Spinney} res. .00005 Soft graphitic H.M. 6 = L F C3 b Sp.{Mr Spinney} res. .00075 and .00128. EFC. | ||