Verant' Stereoscope (various)

interesting compilation of three table model open stereoscopes built for scientific and military purposes, all with adjustable focus and eye base, functional all-metal construction for cards and slides, (1) early version of the Carl Zeiss Jena 'Verant' viewer with tubular oculars and a solid cast aluminium base, in used condition, (2) later version of the same model in good condition, neither Zeiss viewer has its ground glass, (3) boxed French viewer of a similar construction in original fitted box. (3)