A fine 18th-century Dutch brass graphometer, signed on the alidade Johan Eggerich Frers, Fecit Leydie, the protractor-scale finely divided 0 /10 -180 /-195 on the outer scale (off-set by 2½ to the vertical) the middle scale ) -90-0 (x2), with two fixed sights rotating over the protractor scale with fixed compass, set at 90 to the North point, the iron needle finely balanced, with staff attachment and suspension loop, the bridge, fillets and other areas well-engraved with scrollwork, 3 1/8in. (8cm.) diam., 7 5/8in. (19.4cm.) wide