Mark 25 Sextant #025 The top of the line Davis plastic sextant, the Mark 25 features our Beam Converger™ mirror, sometimes referred to as a 'full horizon mirror'. A special coating is applied to high quality optical glass to allow the user to see through this mirror, yet still pick up images as faint as low-light stars. The Mark 25 is illuminated by a long-life LED and made of an upgraded plastic that is very stable. Comes with instruction booklet.