Catalogue entry no. 371 by Max Loehr:
371 Archer’s Wrist Guard(?)
Translucent, pale celadon-green jade object of trapeziform silhouette and like a flattened arc in section. The convex surface is embellished with a series of five transverse ribs, the second and fourth of which connect in a curve at the left side. The third or central rib marks the center of a pointed projection on the right side. Near the left edge, which has not been smoothed completely, are three perforations. Easter Chou(?).
The shape and dimensions of this object would seem to speak in favor of the suggested purpose. Whatever its use in antiquity, in later times it might well have served as a calligrapher’s wrist support.