Silhouette of the Aeronca L16B. The World's Fighting Planes (William Green and Gerald Pollinger, McDonald: London 1954) used 55 Crown Copyright silhouettes provided by the Controller of H.M. Stationery. An acknowledgements section on page 6 of the book identifies them by page. This image is one of those and since the publication date is pre-1957 is in the public domain.
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The World's Fighting Planes, William Green and Gerald Pollinger, McDonald: London 1954