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).
The specifications of a special B coil with condenser paper insulation.
| Identifier | ExFiles\Box 45\4\ Scan010 | |
| Date | 9th March 1921 | |
| X.4079.a EFC. 9.3.21. Herewith special B coil built up with Condenser paper insulation, and 23,000 secondary turns. RHC.{R. H. Coverley - Production Engineer} | ||