BULGARI Tubogas closed necklace in steel and 18k (750 thousandths) yellow gold with almost invisible clasp. Signed Bulgari, Valenza workshop hallmark, 750 thousandths hallmark. Very good hold, supple and rigid at the same time without any deformation. Necklace length: 43 cm. Mesh width: 2 cm. Gross weight: 186.8 g. Bulgari may not be the inventor of Tubogas mesh, but it is the absolute embodiment of it, thanks to a major challenge unprecedented in the history of jewellery: combining gold and steel! In the 1970s, after extensive research, Bulgari found a steel that was normally suitable for aerospace applications, but whose high melting point was compatible with gold, which has a much lower melting point. The difference in malleability between the two metals was such that the number of hours required to manufacture a steel spirotube was much greater and more costly than that required to work with gold. The cost of these hours of work was one thing, but successfully meeting the challenge of matching these two seemingly incompatible metals was quite another. It is one of Bulgari's great victories to manufacture the mesh of this choker that blends the shine of steel with the sparkle of gold, while remaining supple and flexible!