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).
Table of measurements for production push button switches, numbers 11 through 20.
| Identifier | ExFiles\Box 34\3\ Scan033 | |
| Date | 22th August 1919 | |
| 22.8.19. X‡2641. - PRODUCTION PUSH BUTTON SWITCHES X.1627. Switch No. Off-gaps (inches) Carbon contacts. Copper contacts. Copper gap carbons closed. First depression (Carbon contact) Second depression (copper contact) Remarks. 11 .027 .048 .030 .014 TT 12 .025 .060 .044 .013 .047 TT 13 .025 .055 .038 .013 .041 TT 14 .049 .057 .025 .025 TT 15 .037 .054 .029 .019 TT 16 .047 .059 .028 .024 TT 17 .025 .042 .025 .013 TT 18 .031 .047 .026 .016 .036 TT 19 .029 .051 .032 .015 .039 TT 20 .035 ‡058. .035 .018. .045 TT | ||