A key, a safety pin, a balloon, a propeller, a voltmeter - these unexpected objects in art jewelry rewrite the world of the Norwegian "jewelry engineer" Sigurd Bronger. He carries over his fascination for machines and instruments in humorously constructed jewelry pieces, and transforms natural materials and everyday objects into meticulously executed, complex and ingenious constructions. In his Oslo "Laboratorium Mechanum" Bronger works on his witty "carrying devices" - brooches, pendants, and rings with balloons, sponges, eggs, even his mother's gallstones, or with medical equipment, which have a greater positive effect on the mind than on the physical well-being. An established feature of his work, which symbolically marks the entrance into Bronger's world, is the key. This current publication offers such a key; a review of over thirty years of his creative work: from Bronger's experiments with materials and constructions in the struggle with the avant-garde Dutch art jewelry to his attempts in fathoming out states of expansion and emptiness in jewelry. He revolutionized contemporary creative jewelry work in such a way, not just in Norway, where to this day he still finds new forms of expression at the interface of jewelry, art, design and engineering. With works from the 1980s to the present day, the book will carry you off into the humorous world of the decorative engineering art of Sigurd Bronger, one of the most significant Norwegian jewelry artists today. Text in English, German & Norwegian