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).
Specifications for the dimensions and installation of four brushes and their holders.
| Identifier | ExFiles\Box 37\2\ scan 102 | |
| Date | 29th December 1933 | |
| EHT/O.S.P.T.M. H.K. /29.12.33 Contd. -3- There are four brushes, each being .35" x .225" or .078 sq. ins. per brush holder. All brushes are soldered into the holders, and the two negatives earthed. (sgd) C.A.P. | ||