Binoculars Carl Zeiss Jena D.F.8x

Magnification: 8x
Aperture (objective diameter): 20 mm
Field of view: 4.6°
Visible field of view (eyepiece FOV): 36.8°
The closest focusing distance: 6.5 m
Width: 14.9 cm
Height: 12 cm
Weight: 625 g
Production date: 1905.

   Military models of binoculars appeared in Carl Zeiss catalogs in August 1895 – those were O.D.F.95 (Offiziers-Doppelfernrohr 95) with 6x magnification   and D.F.95 (Doppelfernrohr 95) with 8x magnification. However, there are suggestions that first prototypes of these binoculars were produced before 1893, as they had to undergo a long military acceptance (Artillerie Prüfungs kommission - APK). In 1902 these two binoculars were replaced by D.F.6x and D.F.8x, which acquired some modifications.
   The D.F.8x binocular has curved design of upper prism covers, which is called “bent shoulders” and, in fact, it has no visible differences in comparison with its predecessor – the D.F.95 model http://binocollection.com/catalog/binoculars-carl-zeiss-jena-df951.html There is still no explanation for such covers’ shape, according to one hypothesis – it was made for better raindrops dripping, according to another one – it was a distinction from 4x, 6x and 8x civilian binoculars models, also produced at that time.
   However, the two binoculars also have differences (see photo).
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   For example, the clamping screw for adjusting the interpupillary distance has another construction in D.F.8х. Besides, the eyepiece lenses in D.F.8х have diameter 11 mm (this value is equal to 9 mm for D.F.95), although the field of view in both binoculars is the same and equals to 4.6°. The eyepieces’ base diameter is equal to 20.5 mm (this value is equal to 18.5 mm for D.F.95). Since 1902 the binoculars acquired “3/3”-type eyepieces, having a diopter scale (see Hans T.Seeger. Zeiss-Feldstecher, Handfernglaser von 1894-1919, Modelle-Merkmale-Mythos, pp.180-181). The upper prism cover width is 46 mm. This model was also officially purchased by German military people in a private order, as well as officially supplied to the army.
   The binoculars frame hinge is attached to its halves with the help of 5 screws from each side. The upper and lower prism covers are made of brass; the device has long “lugs” for a jugular strap, which are attached to binoculars with the help of 2 screws. The clamping screw for adjusting the binoculars interpupillary distance is of the later type, it has notches and large diameter, which is the proof of binoculars military use. The upper hinge disk is of the 3rd (later type) and it has an interpupillary distance scale (see Hans T.Seeger. Zeiss-Feldstecher, Handfernglaser von 1894-1919, Modelle-Merkmale-Mythos, p.177).
   There are inscriptions “Carl Zeiss, Jenna. D.R.P.” on the left prism cover. D.R.P. is an abbreviation for Deutsches Reichs Patent. There is also an inscription “D.F.8х P.№ 3434” on the right prism cover and it is an abbreviation for Doppelfernrohr 8х Privatnummer 3434. The last inscription means that the binocular has its own number for selling exclusively to military people and in a private order with the permission of military department. The inscription is made in italics and is encrusted with white alloy (silver?).
The binocular coffer has all features of a military coffer of that period: a wide fastening loop for a waist belt, metal side rotary loops for a belt (see photo)
   The serial number of the binoculars is “13676”, it was produced approximately in 1905.