Antique Carl Zeiss Top Mount Achromatic Microscope Condenser 37mm Dia Fit

I've currently just got one of these antique Carl Zeiss top mount microscope condensers with centering and internal iris with graduated scale, as follows. Achromatic 0-10 iris scale, centering, top mounting - no serial number - in fitted red case.

The fit is standard Zeiss 37mm diameter.

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