Davis Instruments 15 Master Sextant Mark 0. The Mark 15 has a 7 (18 cm) frame radius graduated from 120 degrees to -5 degrees and comes with a traditional half-silvered mirror. Comes with an instruction booklet. Specifications for Davis Instruments Mark 15 Master Sextant: Manufacturer: Davis Instruments Color: Black Package Contents: Davis Instruments Mark 15 Master Sextant Davis Instruments 026: 15 Master Sextant Mark