gold ring with turquoise or odontolite

A yellow gold ring set with a turquoise odontolite in a four-petal setting with an inner raised double U. The ring is adorned with decorative curls and arcades around the shoulders mounting, one can also see remains of black or dark blue enamel, end 16th century, European, reported with the Portable Antiquities Netherlands under number: 51328015100.
weight: 2.49 grams
size: 16.75 mm / 6 ¼ US
width: 1 – 7 mm