a grooved ring holding the cover of a watch face or other instrument in position
固定手表(或其他仪表)表面盖的环形凹槽。
a groove holding the crystal of a watch or the stone of a gem in its setting
镶嵌手表水晶(或宝石)的凹形底座。
" late 16th cent.: from Old French, of unknown origin."