in reference to spy-glasses or binoculars, 1905, from the firm founded by German optical instrument manufacturer Carl Zeiss (1816-1888).
Examples from the Web for zeiss
Well, now I will stop, and use my Zeiss glass on the land, which is getting nearer.The Letters of William James, Vol. II|William James
This adjusting of a glass for a fixed distance can be seen with deer-stalking telescopes and Zeiss glasses.The Modern Pistol and How to Shoot It|Walter Winans
At luncheon-time, when I was about half-way, I sat down with my Zeiss glass—my mother's farewell gift—to look for the valley.Prester John|John Buchan
The index of refraction of the above solution may be taken with the Zeiss immersion refractometer or with the Abbe refractometer.All About Coffee|William H. Ukers
See Art. 398 for a description of the Zeiss binocular field-glass for an example of this use of total reflection.Physics|Willis Eugene Tower