VERY GOOD EXAMPLE OF A MID 18TH CENTURY LONDON MADE QUADRANT (OCTANT) INLAID BOXWOOD SCALE 0 TO 90 DEGREES IN 20' DIVISIONS, READING TO 2' OF ARC WITH THE TRANSVERSALS BY THE FIDUCIAL EDGE ON THE INDEX ARM.THE 2 INTERCHANGABLE FILTERS ARE RED, FORE SIGHT & BACK SIGHT, THE THREE MIRRORS ARE DOVETAILED IN THE SLIM BRASS SHROUDS RATHER THAN THE USUAL PRESSURE SCREWS, I BELIEVE THIS TO BE AN EARLY FEATURE, THREE TUDOR ROSES AT EACH END OF THE BOXWOOD SCALE. LOVELY PATINA, PROBABLY MADE BY ADAMS, COLE OR GOATER. 18" RADIUS.