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).
Performance graph showing the daily accuracy error for Smith Motor Type Clocks tested in a lab.
| Identifier | ExFiles\Box 164\1\ img259 | |
| Date | 30th January 1939 | |
| SMITH MOTOR TYPE CLOCKS IN LAB AT 12V MINUTES ERROR PER DAY DAYS +5 0 -5 10 20 30 40 50 60 70 AT 9V R 30-1-39 | ||