9k Gold Bolt Ring Clasp Findings 0.9cm Dia Vintage Art Deco c1920.
The gold mark can be found to the one side this reads '9k'. Good secure clasp with a good spring.
Diameter 0.9 cm or 0.3 inches.
Total length 1.3 cm or 0.5 inches.
Weight 0.3 grams or 0.18 penny weight.