This appears to be an antique or vintage gold-tone stick pin featuring a decorative engraved monogram on a round head.

The back view shows a textured crosshatch pattern on the circular head, along with a secure, right-angle bend attaching the pin stem to the top. The removable metal end piece on the left is a stick pin clutch.

 (or safety protector), which slides onto the sharp tip of the pin to hold it firmly in place and prevent it from poking you when worn on a tie, lapel, or scarf.

Determining the exact market value of a vintage monogrammed stick pin requires evaluating its materials, age, and craftsmanship, as it generally ranges from $15 to $100+.