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).
Rating of the 20 HP engine mounting rubber.
| Identifier | ExFiles\Box 104\1\ scan0041 | |
| Date | 1st January 1929 | |
| X5005 To BY/HEB.{H. Biraben} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}1/LG31.1.29. Herewith rating of the 20 HP. engine mounting rubber as requested. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||