This is a Carl Zeiss konimeter in the collection of an instrument collector in Catalonia.  A konimeter is an instrument for measuring the dust content of a sample of air.  A measured volume of air is drawn through a jet, to impinge on a surface coated with a glycerin jelly.  The dust adheres to the surface and the particles are counted under a microscope.

A manual for the Zeiss konimeter may be downloaded below (12 pages):

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