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).
The confidentiality markings for correspondence related to gun or tank work.
| Identifier | ExFiles\Box 176\2\ img321 | |
| Date | 15th January 1941 | |
| 32 Clerical Department Clan Foundry. Rm.{William Robotham - Chief Engineer}2/EW/15.1.41. All memos and correspondence relating to GUN or TANK work should be marked "Secret" on the letter paper and "Private & Confidential" on the outside of the envelope. Failure to comply with these instructions will be regarded as a very serious matter. Rm.{William Robotham - Chief Engineer} | ||