VERY GOOD EXAMPLE OF AN EBONY OCTANT IN UNUSED CONDITION, THE BRASS-WORK IN ORIGINAL BLACKENED ( OXIDISED ) FINISH, SIGNED: H HUGHES. 59 FENCHURCH ST. LONDON. SCALE MINUS 4 TO 110 DEGREES. DIVIDED IN 20' MINUTE DIVISIONS, VERNIER READING TO 1 MINUTE OF ARC. RADIUS 10" INCHES, INDEX ARM 12" INCHES IN ORIGINAL MAHOGANY KEYSTONE BOX WITH MAGNIFIER. IN MY OPINION THIS HAS NEVER BEEN USED! TWO RED & ONE BLUE COLOURED FILTERS.