Here are most of the swivel or swivel related patents found in the U.S. patent record. Some of these were put into production, others remained a product of the imagination of the inventors as described in these old documents:
US Patent 445747--- US Patent 793751--- US Patent 943299---- US Patent 2322081
US Patent 590749--- US Patent 807100--- US Patent 1050501--- US Patent 2323624
US Patent 651637--- US Patent 815677--- US Patent 1504910--- US Patent 2547124
US Patent 668525--- US Patent 818604--- US Patent 1512367--- US Patent 2548089
US Patent 694664--- US Patent 823595--- US Patent 1591973--- US Patent 2740630
US Patent 698395--- US Patent 868557--- US Patent 1628973--- US Patent 4953852
US Patent 730943--- US Patent 873027--- US Patent 1695829
US Patent 732096--- US Patent 885927--- US Patent 1762439
US Patent 782332--- US Patent 892388--- US Patent 1911065
US Patent 445747--- US Patent 793751--- US Patent 943299---- US Patent 2322081
US Patent 590749--- US Patent 807100--- US Patent 1050501--- US Patent 2323624
US Patent 651637--- US Patent 815677--- US Patent 1504910--- US Patent 2547124
US Patent 668525--- US Patent 818604--- US Patent 1512367--- US Patent 2548089
US Patent 694664--- US Patent 823595--- US Patent 1591973--- US Patent 2740630
US Patent 698395--- US Patent 868557--- US Patent 1628973--- US Patent 4953852
US Patent 730943--- US Patent 873027--- US Patent 1695829
US Patent 732096--- US Patent 885927--- US Patent 1762439
US Patent 782332--- US Patent 892388--- US Patent 1911065
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