Barnard & Gowenlock's Kromaz Stereoscope

rare mahogany stereoscope viewer with three filters (red and blue side-by-side and green below), in very good original condition, filters partially corroded. The Kromaz system patented in England in the late 1890s was a rival to Ives's Kromskop. The system of filters was arranged in such a way that the stereoscopic colour-separation transparencies were laid on a viewer similar in appearance to the Kromskop viewer but in a single step, with label: 'BARNARD & GOWENLOCK'S KROMAZ REGISTERED', very rare, only a few are known to exist