Nikko 10x70

Mfr: Nippon Kogaku Kogyo (Nikko, now better known as Nikon), Japan

Date: WWII

AFOV: ~70 degrees

TFOV: 7 degrees 

Eye Relief: ~18mm

Prisms: high index

Serial Number: 11779

Below: Close-up of eyepieces (note latch mechanism, Japanese characters for left and right on eyecups), yellow filters inserted.

Below:  Wooden case with identification plate (the serial number on the case does not appear to match the binocular).

The Nikko 10x70 was no doubt the most impressive hand held binocular produced by Japan during World War II.  It is said to have been used by airmen.  This would seem to concur with the parachute cord strap and wooden case.  Although uncoated like other Japanese optics of the time, its optical performance is very high.  The objectives are airspaced.  Baffles are incorporated in the objective tube.  I am not able to see any light leakages in the image, though there are ghost reflections from bright light sources that would be reduced by coatings.  The wide field of view has excellent correction, with just a small amount of distortion, field curvature, and astigmatism noticeable at the edge.

The individual focus eyepieces have winged rubber eyecups and an unusual latch mechanism for holding the focus.  The right eyepiece has a reticle with right angle markings (0,20 vertical and 0,20,40,60 horizontal).  Although the eye relief is fairly good, it is not easy to use with glasses due to the eyecups and slightly recessed eyepieces.

It is believed that Bausch & Lomb produced very limited quantities of its own wide field 10x70 based on the Nikko.  If anyone has one of these, I would like to hear from you.