Binoculars Carl Zeiss Jena D.F.6x (5)

   In 1906-1907, Carl Zeiss radically changed the construction and the design of his binoculars (both “civilian” and military ones). Optical characteristics were significantly improved for the new devices (field of view and the lenses diameter were increased, while optical aberrations were reduced), and the devices’ construction was also changed: the central hinge and the “ears” for the neck strap were not attached to the binocular with the help of screws any more - they became the whole part with it instaed, an eccentric lens alignment system appeared and the design of its frame changed, prism covers spanned the binocular body and they were lubricated with a special compound at the joints with the purpose of tightness improvement. In addition, the prisms inside the binocular were no longer pressed by prismatic covers, but they were fixed with special flat springs, which increased the device reliability significantly.
   The new version of military binocular D.F.6х (its old version is available by the following link: https://binocollection.com/ru/catalog/binokl-carl-zeiss-jena-df6x.html) appeared a little bit earlier than its “civil twin” – namely Telex binocular - https://binocollection.com/ru/catalog/binokl-carl-zeiss-jena-telex-6x.html, around the end of 1906. This device became the most popular military binocular of the First World War and its release stopped in the 30s of the last century, before the Second World War. Around 1916-1917, the “D.F.6x” label was changed by “D.F.6x24”. There are several major modifications of this model:
   1st version: 6x21 - the one, where the lens frame and the lower prismatic cover are made as one component (starting from 1906/1907) and having the eyepieces case with the “transverse” knurling (see photo). Nearly 6,000 specimens were produced with such design option https://binocollection.com/catalog/binoculars-carl-zeiss-jena-df6x-2.html.
   2nd version: 6x21 - the one with double-ring type lens frames (starting from 1908/1909);
   3rd version: 6x24 - the one with double-ring type lens frames (starting from 1911/1912) https://binocollection.com/catalog/binoculars-carl-zeiss-jena-df6x-4.html ;
   4th version: 6x24 - the one with rounded objective covers (starting from 1913).
   The presented binoculars refers to the 4th version (rounded objective caps with grooves on the objective covers, intended to minimize stray light ray) and was released in 1914 with a batch of 1060 pieces. The serial number is 416468, an additional military acceptance number (2088) is printed on the side edge of the front right prismatic cover, and there is also the military acceptance mark "K" - "Gewehr-Prüfungskommission" on the central hinge – it is the marking of the Small Arms Acceptance Board, Spandau (Berlin,see photo).
   The “military" use of binoculars is also indicated by the large diameter of the clamp (clamp) of the central hinge (see photo). On the upper disc of the hinge there is an interpupillary distance scale. The grooves (knurling) on ??the eyepieces are located at an angle to each other (“diagonal” knurling), the eyepieces have a diopter scale for sharpening. The width of the upper prismatic cover is 45.5 mm; the height of the binoculars from the lower cut of the lens frames to the upper prismatic cover is 69.3 mm. The diameter of the base of the eyepieces is 20.5 mm.
   There are inscriptions "Carl Zeiss Jena" on the left prism cover. There is also an inscription "D.F.6x 416468" on the right prism cover. The inscription is made in block letters against the background of Carl Zeiss Tessar photo lens schematic image (the earlier models had an inscription in italics until 1904).
   The binocular’s coffer has features peculiar to English coffers of that period (the top cover belt fastener, see photo).
   A later version of this binocular model: https://binocollection.com/catalog/binoculars-carl-zeiss-jena-df6x24.html