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).
List of seven single variations from the standard for tungsten contact point experiments.
| Identifier | ExFiles\Box 61b\1\ scan0100 | |
| Date | 29th May 1930 | |
| X2894. 29.5.30. X.2894. TUNGSTEN CONTACT POINT EXPERIMENTS. SINGLE VARIATIONS FROM STANDARD. (1) Reversal of current supply. (2) Stronger spring. (3) Platinum screw point. (4) Platinum lever point. (5) Domed screw point. (6) Three flat cam. (7) Maximum value condenser. EFC. | ||