The exhibition 'Jewel in the Crown of the Commonwealth. Decorative Art of Royal Prussia', opened from December 2006 to May 2007 in Zielona Brama, one of the seats of the National Museum in Gdansk and a former Gdansk residence of the Polish monarchs, continued a series of expositions presenting the artistic legacy of Royal Prussia, i.e. the region of Pomerania historically encompassing the former state of the Teutonic Order in Prussia, Gdansk Pomerania, part of Central Pomerania, and Warmia. The framework of the exposition included the Thirteen Years' War, the grant of major privileges to Gdansk by King Casimir IV Jagiellon, and the first partition of Poland in 1772 when Gdansk, together with Pomerania, fell to Prussia. The exhibition featured artistic objects which for the inhabitants of Royal Prussia were either utilitarian or reflected the social status and taste of their owners. Amber, gilded and white silver products, as well as inlaid or incrusted items were also treated as capital investment, a way to inspire admiration and build prestige. The display gathered exhibits from 14 domestic and seven foreign museums, more than ten cathedral, parish and rector churches, two cloisters, a private collector, and priceless manuscripts and graphic art from the collection of the Gdansk Library at the Polish Academy of Sciences. 49 authors presented the outcome of their research in almost 700 entries in an illustrated two-volume catalogue. The exhibition showcased representative groups of amber objects, liturgical goldsmithery, luxury, guild and table silverware, furniture, clocks, cloths and embroidery, iron, copper, brass, tin, bronze and bell-founding objects, as well as ceramic products divided into tiles and vessels. The event presented a wide selection of guild production in the larger and smaller centres of Royal Prussia. The exhibition made it possible to scientifically analyse nearly half of the presented objects for the very first time. This group includes furniture, pottery, smithery and foundry objects, as well as goldsmithery, the pride of the Gdansk, Elblag and Torun workshops. Out of the 234 presented goldsmithery objects, 55 have not been previously analysed, i. a. the works of Gdansk goldsmiths on loan from Focke Museum, a department of Bremer Landesmuseum fur Kunst und Kulturgeschichte and Galerie Neuse-Kunsthandel in Bremen, as well as the collections at the National Museum in Warsaw. The exhibition comprises a lasting contribution of Gdansk museology to national cultural and scientific legacy.