Pin Art Nouveau Diamond and Enamel Orchid Pin. Art Nouveau Diamond and Enamel Orchid Pin (Reverse). A pin is a small decorative jewelry item designed to be affixed to a garment by means of a pinstem. The pinstem is a jewelry finding composed of a sharp object that is designed to pierce fabric in order to secure a brooch/pin in place. Related Reading Brooch Art Nouveau Diamond and Enamel Orchid Pin. Art Nouveau Diamond and Enamel Orchid Pin (Reverse).