Andrew Nethercott Antiques has dated this piece to the 1870s.

The pin and hook are designed to be removable, possibly to fit as a bracelet slide.
The frame is unmarked but tested as solid 15-18 carat gold
Overall height 2,3/8" or 62mm, weight 23 grams.
All in excellent condition with no damage or repair noting a replaced silver pin and mount.
Andrew Nethercott Antiques has dated this piece to the 1870s.
Works of art, collectables, scientific and decorative antiques from the 17th - 20th century
You can view the stock and full dealer information on the Andrew Nethercott Antiques Profile Page