German Army World War II Era Dienstglas 6X30 Binoculars. During the war binoculars were expensive and strictly army property, which is why the (obscured) inscription translates to "Service Glass." The first number of 6X30 indicates the magnification level, and the second number indicates the diameter of the objective lens in millimeters. The "dds" below indicates the maker of the binoculars: Voigtlaender u. Sohn AG, Braunschweig. 

Condition: Scratches and marks on body and lenses. Commensurate with use and age. 

Size: 6 1/2 x 4 1/2 x 1 1/2 in. 

#4766 . 

Binoculars (or field glasses) are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. Most binoculars are sized to be held using both hands, although sizes vary widely from opera glasses to large pedestal-mounted military models. Unlike a (monocular) telescope, binoculars give users a three-dimensional image: each eyepiece presents a slightly different image to each of the viewer’s eyes and the parallax allows the visual cortex to generate an impression of depth. Almost from the invention of the telescope in the 17th Century the advantages of mounting two of them side by side for binocular vision seems to have been explored, and most early binoculars used Galilean optics, with a convex objective and a concave eyepiece lens. The Galilean design has the advantage of presenting an erect image but has a narrow field of view and is not capable of very high magnification. This type of construction is still used in very cheap models and in opera glasses or theater glasses. An improved image and higher magnification are achieved in binoculars employing Keplerian optics, where the image formed by the objective lens is viewed through a positive eyepiece lens (ocular). Since the Keplerian configuration produces an inverted image, different methods are used to turn the image the right way up. But the binoculars with erecting lenses had a serious disadvantage: they are too long. Such binoculars were popular in the 1800s, but by the 1890s they were superseded by prism-based technology, which has dominated the form ever since. Optical prisms added to the design enabled the display of the image the right way up without needing as many lenses, and decreasing the overall length of the instrument, typically using Porro prism, named after the Italian inventor Ignazio Porro. Today binoculars can even be made in extremely compact styles suitable for almost any daytime activity from tourist attractions to bird watching, and even night vision and electrical innovations have made them usable at any time of day.

Scratches and marks on body and lenses. Commensurate with use and age.