Binoculars Carl Zeiss Jena D.F.03. (1)

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: 3.2 m
Width: 15.4 cm
Height: 10.5  cm
Weight: 520 g
Production date: 1915.

   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.
    In 1908, one of Carl Zeiss main competitors in the military optics market, the German company C.P.Goerz, released another version of 6x24 binocular marked “D.F.03” (the model had been produced since 1903). The binocular became very popular and, apparently, that was the reason why Carl Zeiss announced the start of the same model production at his factory in March 1911, which was mentioned in a letter to the Bavarian Royal War Office (Munich). The Carl Zeiss D.F.03. binoculars was a complete analogue of the already popular Carl Zeiss D.F.6x model. 
   This device was not produced as massively as the D.F.6x (D.F.6x24) and today two modifications of this binocular are known among collectors:
   1st version: 6x24 - the one with double-ring type lens frames (starting from 1910)
   2nd version: 6x24 the one with rounded objective covers (starting from 1913);
   The presented binocular belongs to the 2nd version (with double-ring type lens frames and with the grooves intended to eliminate side stray light - see photo). The binocular’s “military" application is proved by the large diameter of the central hinge clamp (lock) and the cover presence, which was intended to protect eyepieces from rain – the so-called “raincoat”. The interpupillary distances scale is indicated on the upper hinge disk. The eyepieces’ grooves (the knurling) are located diagonally to each other (the “diagonal” knurling). The eyepieces have a diopter scale for sharpness adjustment. The upper prism cover width is equal to 45.5 mm; the binocular’s height from the lens barrel lower cut to the upper prism cover is equal to 69.6 mm. The eyepieces’ base diameter is equal to 20.5 mm.
   There are inscriptions “Carl Zeiss Jena” on the left prism cover. There is also an inscription “K.B.Dienst-D.F.03. Nr.15450” on the right prism cover. The inscription is made in block letters with the help of silver alloy. “K.B.Dienst” (königlich bayrisches) - the binocular was made for the Bavaria Royal War Office. What the numbers “12485” and “25710” mean, is still unknown, perhaps these are the military acceptance number. There is also another inscription without explanation on the front right prism cover – namely “III/11”. Perhaps this is the unit number in which the binocular owner served. The prism covers are made of brass and they are attached to the binocular with the help of three screws.
   The serial number “461359” is located on the upper right prism cover edge (see photo). According to Hans T.Seeger book Zeiss-Feldstecher, Handfernglaser von 1894-1919, Modelle-Merkmale-Mythos, p.834) this number belongs to a 700 pieces’ batch (numbers 461001-461700), made in 1915 and marked as the unknown model - “?” in the book. It is likely that this was exactly the D.F.03 binoculars batch.
   The binocular is equipped with original military coffer with “Carl Zeiss Jena” embossing. The Carl Zeiss Jenna D.F.03. “twin”-binoculars C.P.Goerz D.F.03 were equipped with similar coffers. Probably the coffers for these binocular models Carl Zeiss Jenna and C.P.Goerz were not manufactured on their own, but were purchased from a third-party manufacturer.