This is a Ross wide angel binocular 3 1/2 is the magnification power of the set.
It was used on AA guns but more often on Radar positions linked to AA guns, in the trainers and layers positions.
The sets came in two types, that which could be focused and fixed focus, this example is the less commonly seen "fixed focus" type.
Completely waterproofed with anti-glare filters in the front hood the optical quality is very good.
Ross provided a number of director's binoculars to the Royal Navy in WW2, all very good quality.he link to the set which is for sale , the vendor is asking £825 for them, I honestly don't know where he got his price it is insanely unrealistic, I would expect to pay £150-200 for a set.(£825 is not even in the ball park.)
These sets appear for sale quite often on eBay , price and condition often vary and are very underestimated amongst collectors. The "NP45 " , refers to the year in which this set was tested by "the National Physics Laboratory (1945).
Ross also supplied directors binoculars were also supplied in 7x50 and 10x70, and binoculars in 10x70 and 10 x80 , all are very good quality.
Hoping this is helpful.
Attached show the set mounted on a radar director's position on HMS Prince of Wales, dated April 1941, her working up exercises.
