Winterthur's SRAL used XRF to measure the gold alloy on September 19, 1988 according to request 2298-B: Copper 8.8% Silver 9.6% Gold 81.6%
Analysis concluded that this ring is 20K gold and has a weight of 2.28g.
Bibliography and Bibliographic Notes
Book: Swan, Susan Burrows. 1977 Plain & Fancy: American Women and Their Needlework, 1700-1850.