Binoculars Carl Zeiss Jena Silvarem 6x (2)

Magnification: 6x
Aperture (objective diameter): 30 mm
Field of view: 8.4°
Exit pupil diameter: 5 mm
Visible field of view (eyepiece FOV): 50°
The closest focusing distance: 3.8 m
Width: 16.7 cm
Height: 11.8 cm
Weight: 760 g
Production date: 1913.

   Binoculars with central focusing appeared on the market in the middle of the 19th century. Carl Zeiss engineers were not in a hurry with such devices’ production, since they considered them less reliable and protected from dust and dirt. First prototypes of these binoculars were produced in Jena back in 1907, but only in 1909/1910 Carl Zeiss was forced to begin mass production of the devices of such design under the competitors’ pressure and because of the demand. First models of central-focus binoculars appeared in T136 catalog in 1910–those were Teletur 6x15, Telexem 6x21, Telactem 8x24 and Silvarem 6x30. Subsequently, all civilian Carl Zeiss binoculars with central focusing had an “...em” ending in their designations.
   The Silvarem 6x(30) binocular turned out to be very good in design and optical characteristics and it was produced from 1909 to 1969.
   The presented rare specimen belongs to the second version of this model (which was produced for a short period of time from 1911 to 1913/14) and it has the following peculiarities:
   - the binocular’s design has a long body and short frames of the two-ring type lenses;
   - the prismatic covers are fastened with the help of three screws;
   - the central focusing eyepiece bridge arms are of the fork design (see photo), they also have a large thickening closer to hinges and are made of brass;
   - the eyepieces’ front lenses diameter is equal to 13.7 mm, the binocular’s field of view is equal to 8.4 °
   The binocular’s design has changed since 1913/14: the lenses with rounded objective covers have appeared. The binocular’s field of view has also increased slightly (up to 8.5 °), but the eyepiece’s front lens has been decreased to 11.5 mm), the central focusing bridge arms’ design has changed (its thickness has been decreased).
   The binocular’s “civilian” application is proved by the central focusing mechanism and the central hinge fixture’s (clamp’s) small diameter (see photo), which has a hole for a knob (included to binocular’s delivery kit), with the help of which the hinge could have been finally fixed depending on the observer’s interpupillary distance. The interpupillary distances scale is indicated on the upper hinge disk. The right eyepiece has its own focusing mechanism with a diopter scale.
   The base diameter of this device’s eyepieces is equal to 24.5 mm and the upper prism cover width is equal to 52 mm (see photo). The eyepieces have a longitudinal knurling. The binocular’s case height (including the upper prism cover) is equal to 77.3 mm; the binocular’s height without lens frame is equal to 66.5 mm.
   There are inscriptions “Carl Zeiss Jenna” on the left prism cover. There is also an inscription “Silvarem 318266 6x” on the right prism cover. The inscription is made in block letters with the help of silver solder on the background of Carl Zeiss Tessar photo lens schematic image.
   The binocular’s case has features peculiar to models of that period of time (see Hans T.Seeger. Zeiss Handfernlaser 1919-1946, Modelle-Merkmale-Mythos, pp. 607-627): the top cover short fixture to the case (the “civilian” binocular models’ peculiarity), the upper carrying handle remnants, the Carl Zeiss Jena logo.
   The device’s serial number is 318266; it was manufactured in 1913 as a 300 pieces batch.
   The previous rare version of this binocular with long frames of the two-ring lenses’ type:
   It was replaced by:
   The similar design binocular’s model with separate focusing, namely Silvamar 6x, can be checked by the following link: