Amazon.com: Winner Retro Manual Mechanical Skeleton Watch 。Elegant vintage skeleton watch with rubies (likely synthetic), *see below. Black leather strap. Unique dial design. Gold colored casing and half white, half see-thru face with a unique magnifying glass cylinder on top. Full mechanical exposure on back. No battery required, manual wind. Black leather wrist band. *In a mechanical watch movement, there are many gears, pivots, and pinions that need to rotate smoothly and with minimal friction. This is where jewels come in. Typically by synthetic sapphire or ruby, these gemstones are meticulously placed in specific locations within the movement. The pivots of the gears are mounted on these jewels, allowing them to rotate freely and smoothly. This reduces the friction between the moving parts, resulting in improved accuracy and longevity of the watch. The use of jewels in watch movements is a testament to the meticulous craftsmanship and engineering precision that goes into creating these timepieces. so lovely so unique