Cup seamer, c 1950s. A cup seamer is used in hosiery manufacture for joining the edges of knitted fabrics, as in seaming fully-fashioned stockings. It is a three-thread chain-stitch machine employing a needle and two loopers. On the base are two treadles for operating the motor clutch and opening the feed cups. The machine sews 3000 stitches and 9 feet of seam per minute. It was manufactured under US patents (dated 1936, 1941 and 1948) by the Union Special Machine Company, successor to the Grover and Baker Sewing Machine Company - the originator of the double chain-stitch machine.