Founded in 1862 in Hamburg, the Plath Company was a German manufacturer of high-quality sextants, compasses, and other navigation instruments. The Plath sextants were especially prized for their accuracy and craftsmanship. While sextants could be manufactured for either navigation or astronomy, Plath focused on marine sextants, and its sextants were often used by the German Kriegsmarine (Navy). Marine sextants have played a crucial role in navigation, especially before the advent of GPS and radar.

Sextants are instruments used to measure the angle between two visible objects. The primary function of a sextant in maritime navigation is to help determine a ship's latitude and longitude. The first step is to use a mirror and scope to sight the horizon. After aligning the instrument with the horizon, a celestial object (such as the Sun or a star) is viewed through the eyepiece. A moving index arm is adjusted until the reflection of the celestial body is brought down to touch the horizon. The angle between the horizon and the celestial body is read from the graduated scale on the instrument. The measurement of the angle provides the altitude of the celestial body above the horizon. The time of the observation is also needed to determine a ship’s position.