The Armin Strom Skeleton Pure 'Elements' collection was introduced in 2014. While all the brand's watches are openworked to some degree, the Skeleton Pure takes it to another level with a fully skeletonized version of caliber ARM09 -customized in accordance with respective themes of the four limited editions available.The Skeleton Pure 'Earth', reference ST15-PE.40, features bridges with a black PVD coating. The off-set dial ring is made of sapphire. The stainless steel case is PVD-coated.