Two examples of exhibition circles by Klaus Kemp (25 diatoms in each). Mounted in Hyrax, and dated September 1991 and both with some debris in the mountant.
Olympus BHB microscope using 450nm LED light. 20x Nikon Plan Apo 0.65 objective. Olympus Aplanat Achromat condenser, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. Images stacked in Zerene (Pmax).
The first has a gold dot on the slide.
There has been some movement of the diatoms on the slide. I did minimal tidying up of the debris on the slide.
The second has a similar label, but no gold dot. I spent more time to tidy up the background on this one.
The two slides are quite similar with the species on them (although not identical). Some interesting diatoms on them both which warrant some additional high resolution imaging.