late 17th century, signed 'N. Bion a Paris', a small and highly decorative example with pierced foliate engraving, hand engraved and divided to half a degree, fixed sight vanes and rotating alidade with twin sights and twin index readouts, 16 point compass rose with compass also divided to two degrees, staff mount below, suspension point at 90 degrees to allow vertical as well as horizontal use, in fitted walnut case, width 19cm