This very Victorian pin is gold fill set with two rose-cut red pastes and one cabochon ‘turquoise’. The pin is 1 ¼" wide with a central ball element that is 3/8" in diameter.
Applied circles of wire rope ornament a vertical, rectangular bar. A hollow ball dangles from two chains; another chain connects the pin to the stickpin. This device preceded the safety catch to prevent loss of the pin.
The C hinge and double C catch are replacements. The pin bears a Maker's mark OB, which stands for Ostbye and Barton Company, Providence RI. This company was started in 1880, and was the largest jewelry manufacturer and largest ring manufacturer in world.
Irrelevant but perhaps interesting note: Ostby was on the Titanic.