Binoculars Carl Zeiss Jena D.F.03.

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: 3.7 m
Width: 15.4 cm
Height: 10.5  cm
Weight: 460 g
Production date: 1910.

   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 device was intended primarily for junior officers (there is an inscription“U.F.” on the right prismatic cover (non-commissioned officer)).
   However, there are two interesting facts. The first one is the following: the Carl Zeiss D.F.03. Dienstglas model was a complete analogue of the already popular Carl Zeiss D.F.6x model The question arises: what is the reason of producing the same models under different designations? Perhaps, Carl Zeiss decided to keep up with his competitors that way. The second point is the following: according to the letter addressed to Munich (see above), they started to produce the Carl Zeiss D.F.03. Dienstglas model in March 1911, but the device we are considering has serial number “205905”, which was produced as a 600 pieces batch in the second half of 1910 (numbers 205601-206200). According to Hans Seeger (see Hans T.Seeger. Zeiss-Feldstecher, Handfernglaser von 1894-1919, Modelle-Merkmale-Mythos, p. 808), this batch of binoculars is marked as the unknown model - "?". Obviously, Carl Zeiss started producing the D.F.03. binoculars back in 1910.
   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 1st version (with double-ring type lens frames). The binocular’s “military" application is proved by the large diameter of the central hinge clamp (lock). The interpupillary distances scale is indicated on the upper hinge disk. The eyepieces’ grooves (the knurling) are located perpendicularly to each other (the “perpendicular” 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 Jenna” on the left prism cover. There is also an inscription “D.F.03. Dienstglas Nr.12485 U.F.” on the right prism cover. The inscription is made in block letters with the help of silver alloy. “Dienstglas” is a military (service) glass. What the number “12485” means, is still unknown, perhaps it is the military acceptance number. The prism covers are made of brass and they are attached to the binocular with the help of three screws.
   The second version of this binocular model can be checked by the following link: