Blueprint showing two designs for car bonnet louvres.
| Identifier | ExFiles\Box 119\3\ scan0173 | |
| Date | 4th November 1931 guessed | |
| COLT VENTILATION LTD. BUSH HOUSE, LONDON, W.C.2 Protected by World Patents and Car bonnet louvre DRG NO. DATE TRACED BY CHECKED BY AND APPROVED BY COLT VENTILATION LTD. | ||
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).