What does 21 jewels mean on a watch?

On a watch, 21 jewels means that the timepiece has a particular type of movement. Specifically, the movement features 21 jewel capstones that serve as bearings, allowing the gears inside to turn. Typically, only high-end mechanical timepieces feature 21 jewels, with 17 jewels being more common. Find a diverse assortment of watches from some of the world's top sellers on 1stDibs.