BINO PRISM Mk4 6E/383 5×40 RAF Spotter Binoculars with Fixed Focus. No.8353


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This is a pair of vintage British BINO PRISM Mk 4 6E/383  5×40 RAF spotter binoculars with serial number 8353. These binoculars are in good working order.

Some Main Features:


Model: BINO PRISM Mk4  6E/383  5×40 spotter binoculars

Magnification: 5 x (note: magnification is not marked on binoculars, but according to research from the web, these Bino Prism Mk4 6E/383 binoculars were 5×40 WW2 RAF spotter binoculars models, see note below)

Objective lens diameter: 40mm

Eye lens diameter: 17mm

Fixed focus (i.e., no need to adjust image focus while using the binoculars, an important feature for aircraft spotting, see note below).

Serial number: 8353

Dimensions (when binoculars fully open): 180mm (W) x 190mm (H) x 65mm (D)

Solid metal body construction with admiralty style thick layer of black paint protection.

Net weight: approx. 1.05 kg

Comes with leather neck strap.

The binoculars are in good working condition with correct collimation and nice images for their age.

General wear and tear appropriate with age and services.

Note: According the some information from the web, the manufacture is Ross and the Model is “Bino. Prism Mk4  6E/383 5×40”, with good condition, lens Clear and clean no marks or scratches. The “B” marking on right prism cover indicates the optics are “bloomed”, i.e. coated, and the marking “6E/383” is a Royal Air Force stores code for this type of instrument. This is a fixed focus aircraft spotting and maritime reconnaissance including U-boat spotting binocular. It is reported but not confirmed that it was used by observers in Beaufighters and other nightfighters during WWII. The Mk.IV was built by Ross under Royal Air Force contract, introduced in 1941, and continued to be used at least into the 1960’s. It was succeeded by the 5×40 6E/392. It is the first British war-time binocular to employ coated lenses. According to a 1943 report by the Admiralty Research Laboratory, the x5 Mk. IV’s 8 mm exit pupil gave10%, 15% and 25% “improvements” (in light transmission) under respectively half-moonlight, starlight and dark conditions compared to a 7X50 Admiralty Pattern 1900 (probably a Barr & Stroud CF41). 

Please see photos for further details.

More information on How to identify or estimate the production dates of vintage binoculars.

Additional information

Weight 1.5 kg


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