The setting also has has three leaves in gold on each side of the center cabochon.
The ring is a size 9 and 3/4" along the finger, the cabochon is a very deep 1/3" with some scratching visible under magnification, some paint missing inside as can be seen in the photos.
The band, which may be later-added, is hallmarked for 9ct gold, "375", maker "T&S", "9 375 R" in a hexagon mark, cabochon tests as rock crystal, band tests 10k, cabochon setting tests 14k.
NOTE: That is my windows reflected in the left side of the dome.
Although jewelry is sometimes seen with a much later inscription, that is not the norm.Stones in the rings could also be set in a silver head with a karat gold band and rose cut diamonds, all typical of this time period.Hair and memorial rings were worn by both men and women.The diamond is 3.3 to 3.6 mm, difficult to measure in this setting.The color is a foil backed light brown and it has a tiny broken edge visible only under magnification.