.41 Rimfire. 2.5" barrel length. SN: 6312. Blued metal finish with silver plated frame and triggergouard mounting walnut birdshead stocks with bordered checkered butt and engraved embellishments. Single shot single-action sliding barrel derringer pistol with half cock safety and front blade and rear hammer notch sights. Left barrel is struck WILLIAMSON'S PAT. OCT. 2. 1866 NEW YORK with upper barrel engraved with an {Arrow} mark to instruct users in basic operation. The frame and triggerguard feature spiral scrollwork with sunburst to forward frame.