The German gem-engraver, medallist, and amateur scholar Lorenz Natter (1705-1763), was so impressed by the size and quality of the collections of ancient and later engraved gems which he found in Britain that he proposed the publication of an extraordinarily ambitious catalogue &; Museum Britannicum &; which would present engravings and descriptions of the most important pieces. He made considerable progress to this end, producing several hundred drawings, but in time he decided to abandon the near completed project in the light of the apparent lack of interest shown in Britain. Only one of the intended plates in its final form ever appeared, in a catalogue which he published separately for Lord Bessborough&;s collection. On Natter&;s death the single copy of his magnum opus vanished mysteriously, presumed lost forever. All hope of recovering Natter&;s unpublished papers seemed vain, and their very existence had come to be doubted. Yet they were to be found more than two hundred years after his death, in Spring 1975, when the classical scholar and renowned expert in gems, Oleg Neverov, chanced upon them at the bottom of a pile of papers in the archives of the State Hermitage Museum in St Petersburg. Neverov and his colleague Julia Kagan carried out the initial research on the Hermitage manuscripts and produced the first published account of this archival treasure. The present volume builds upon their earlier work to produce the first comprehensive publication of Museum Britannicum, offering full discussion in English and presenting Natter&;s drawings and comments alongside modern information on the gems that can be identified and located through fresh research. This book is the result of a ten-year collaboration between scholars on the Beazley Archive gems research programme at Oxford&;s Classical Art Research Centre and the State Hermitage Museum. It fulfills Natter&;s vision for the Museum Britannicum &; albeit two and a half centuries late &; to the benefit of art historians, cultural historians, curators, and gem-lovers of today.