This 7x35mm Prism telescope fits Tamaya, Astra IIIB and C. Plath sextants. The increased magnification of this scope allows the sun's diameter to appear larger. It also better defines a distant horizon as seen from a ship, helping the navigator determine the point of tangency of the Sun's limb and the horizon. The most important feature of a scope is the fork (sometimes called a rising piece) which should be exactly perpendicular to the optical axis. The fork on this scope is cast as part of the aluminum body, and has no error of perpendicularity.