Estimate: $650 - $1,000
16-inch radius mahogany octant, marked Tobias Black on ivory plaque on the crossbar, with boxwood scale divided -2 to 99, mahogany and brass index arm, boxwood vernier scale divided 0-20, brass thumbscrew lock, brass sighting vane, mirrors, and shades (blue, red, green), ivory pencil cap to crossbar and writing plaque to verso. Late 18thC. On display easel. Sold at Cordy's pre-1985. Provenance: The H.N.E Sheppard Estate Collection.