I HAVE HUNDREDS OF TIE TACKS, TIE BARS AND CUFF LINKS. cuff links: 0.69" x 0.44" (approx. 11/16" x 7/16" or 17mm x 11mm). I always try to point out any clear blemishes and condition. 0.50" = 1/2" or 12.5mm -this is fairly large for standard button holes.
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