An arrangement of four Coscinodiscus concavus. No information on location or mountant. No makers name, although the style is similar to Wheeler or Watson and Sons. Three of them are in one orientation with the top side facing upwards and rim down, and one (the top middle one) is the other way up with the rim towards the coverslip. Olympus BHB microscope using 450nm LED light. I chose 2 for imaging further (the smaller two in the middle of the arrangement). 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, slightly oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. Image stacks prepared in Zerene (Pmax) – 22 images for the one with the top side facing upwards, and 26 images for the one with the rim facing upwards. The one with the rim/underside facing the camera shows a faint radial pattern in the stack. This is more obvious when looking at a crop of a single frame before stacking, where the contrast has been boosted.