Centering an opal measuring app. 10 x 7 mm, flanked by Old European cut diamonds weighing app. 0.06ctw, measuring app.1 1/16 x 1 1/8 inches, fashioned in 14k yellow gold. Krementz. Circa 1900. Similar example on page 219 of C. Jeanenne Bell's Answers to Questions About Old Jewelry.*Although vitreous enamel forms a hard, durable surface, it is susceptible to chipping and breakage upon impact.