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).
Test observations of spark and arc characteristics under various conditions.
| Identifier | ExFiles\Box 63\4\ scan0014 | |
| Date | 26th May 1918 guessed | |
| (14) Z/2000/2/A/A Same as for 600 R.P.M. (...) ZA2/2000/2/A/B Spark and arc. (63) ZA2/2000/2/R/A Ditto. No. difference between adv. and retd. (64) ZA2/2000/2/R/B Sparks & arc Less "snappy" than for advan (65) ZA2/2000/5/A/A Same as for 600/5 No diff. again between A & R.{Sir Henry Royce} (66) ZA2/2000/5/A/B Spark ok Spark & trace of arc Missing. | ||