Warning: This pin is lethal. It should not be worn or stored anywhere near children or temperamental people. The dagger comes out of the sheath and is extremely sharp.
This pin in the form of an ornate dagger sheath, rife with caviar beading and scrollwork, a wavy dagger with ornate hilt that is connected to the sheath with a fine chain. It has a C clasp on the back. The pin is silver although not marked and I don't believe it is solid silver. The blackening is deliberate and not just the tarnish of the ages. It is 2.25 inches long.
I know nothing about this pin. It seems to me that it might be a ceremonial piece, part of a religious ritual or costume or a pin-sized replica of a ceremonial dagger. If you know more, I'd love to hear from you.