These earrings are marked Siam Sterling. They are clip style and made of sterling silver with niello enamel applied around the design of Balinese dancers. This effect is much like cloisonne or Damasquinado de Toledo except in silver instead of gold.
The earrings are 1 5/8 inches and in excellent condition.
Age is difficult to assess. Thailand was known as Siam until 1939 and then again from 1945-49. My guess is that these from the late 1940s or 1950s. Most earlier earrings were either pierced or screwbacks.
I gladly combine shipping. Combining items with shipping included earns you a bit of money back.