Negretti Zambra field glasses identification help please

[Mike Bolan]

My wife found these binoculars in a charity shop and we were hoping to identify them. Google searches offer either WW1 field glasses or opera glasses. 
Identifying marks are: Negretti Zambra Opticians London and Holborn Viaduct 45 Cornhill 22 Regent Street.

would any of you experts be able to help with identification 

many thanks

[Chasemuseum]

Would favour opera glasses given the distance between the lenses and yes, I am aware that there is a telescoping function and that the binoculars are shown in the compact position.

[MikB]

These are Galilean glasses most likely made in the late 19thC., although Dollond were still selling them as late as 1926.

They have a general resemblance to British Army Binocular, Mk.V., but have a narrower focussing wheel - not sure if they have pull-forward rayshades to avoid reflections glinting off the objectives. If these are patterned after the Mk.V, their magnification might reach 4.5x, but most Galileans were less powerful. Some models had achromatic 2-element objectives - this can be tested by looking at the objectives held at an angle to a light source - if you can see three or more reflected images of the light, then there are multiple air-glass surfaces. For a high-status instrument shop like N&Z to accept them it seems more likely they would be achromatic.

Although N&Z were obviously prepared to put their name on them, and advertised proudly that every part of their telescopes were made in their factory at Half Moon Works, Barnsbury N1, this might not have applied to binos, and many such instruments might be imported from France. 'Badge Engineering' is not a new thing.

Galilean glasses were significantly outclassed by prismatic models starting with the Zeiss 'Feldstecher' of the early 1900s, in both magnification and field of view. However, they retained a military usefulness in some conditions because they were more forgiving of defective eyesight (especially short-sight) than prismatics, and their light grasp in poor light could be better. Some were accepted for military use during the early WW1 emergency when the British services were critically short of optical equipment - if that's so they may be marked 'S.3' or 'S.4'. Even if they're not so marked they may well still have been taken to the front as a private purchase or family donation.

Opera glasses are often decorated with mother-of-pearl, highlights of silver or other bright metals, coloured leather or enamels. What finish is left on these looks much more utilitarian.

 

Edited 9 September , 2023 by MikB

[depaor01]

As an oldtimer on this forum I'm occasionally stunned by the knowledge and detail in some replies. This is one. 

Well impressed @MikB!

Dave