What is an ornamental button of various forms, worn in a shirt front, collar, wristband, or the like, not sewed in place, but inserted through a buttonhole or eyelet, and transferable called?

stud — An ornamental button of various forms, worn in a shirt front, collar, wristband, or the like, not sewed in place, but inserted through a buttonhole or eyelet, and transferable. (Webster's 1913.)

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