Binoculars Carl Zeiss Jena D.F.6x24

Magnification: 6x
Aperture (objective diameter): 24 mm
Field of view: 6.8 °
Visible field of view (eyepiece): 41°
Plasticity: 1.75
The closest focusing distance: 2.5 m
Width: 14.5 cm
Height: 10.5  cm
Weight: 480 g
Production date: 1918.

   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/catalog/binoculars-carl-zeiss-jena-df6x.html) appeared a little bit earlier than its “civil twin” – namely Telex binocular - https://binocollection.com/catalog/binocular-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-1.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);
   4th version: 6x24 - the one with rounded objective covers (starting from 1913).
   The presented binocular refers to the last, 4th version (with rounded objective covers) and it was released in 1916 as a 2000 pieces batch. The serial number is 840739 and there is no additional military acceptance number.
   The binocular’s “military" application is also proved by the large diameter of the central hinge clamp (lock) (see photo). The interpupillary distances scale is indicated on the upper hinge disk. The eyepieces grooves (knurling) are angled to each other (“diagonal” knurling), the eyepieces have a diopter scale for acutance adjustment. The upper prismatic cover width is 45.5 mm; the binocular height from lens frames’ lower cut to upper prismatic cover is equal to 69.3 mm. The eyepieces base diameter is equal to 20.5 mm.
   There are inscriptions “Carl Zeiss Jenna” on the left prism cover. There is also an inscription “DIENSTGLAS D.F.6x 840739” on the right prism cover. The inscription is made in block letters (early models had an inscription in italics until 1904) on the background of Carl Zeiss Tessar photo lens schematic image. The prism covers, the upper hinge disc and the eyepieces’ bodies are made of zinc alloy (Germany felt shortage of non-ferrous metals at the end of the war: those parts were made of brass earlier). The prism covers are attached to a binocular carcass with the help of one screw (previously, three screws were used).
   The binocular’s coffer has features typical for English production civilian coffers of that time: velvet interior, specific top cover fastener, absence of rivets (see photo). Probably, the coffer does not belong to this binocular and it has another origin.
   The previous version of this model without zinc alloy application in the construction and with the marking “6x” is available by the following link:  https://binocollection.com/catalog/binoculars-carl-zeiss-jena-df6x-3.html