This is a vintage or antique brass picture button with an Art Nouveau design, likely featuring a lily of the valley motif.

The design has detailed relief and appears to be made of metal with an antique brass finish.

It is likely a shank button, designed for sewing onto clothing or use in crafts.

Similar buttons are often found in vintage or antique collections and lots.

The style suggests a possible origin in the late 19th or early 20th century.