This is an antique bar brooch with safety chain, dating to the late Victorian–Edwardian period (c. 1890–1915).

What it is
    •    Type: Bar brooch (also called a stock pin brooch)
    •    Stone: A faceted yellow gemstone — most commonly citrine
    •    Setting: Open-back oval collet/claw setting
    •    Metal: Likely 9ct or 15ct gold, or rolled gold (the warm tone and construction are period-correct)
    •    Feature: Safety chain — a strong indicator of genuine antique origin

Design details that date it
    •    Rope-twist circular accents on either side
    •    Slim horizontal bar form
    •    Hand-cut gemstone facets (older style, not modern precision)
    •    Original fitted velvet presentation box (big plus)

How it was worn
    •    On a high-neck blouse, lace collar, or cravat
    •    The chain clipped to fabric as insurance against loss (very common pre-WWI)