Coscinodiscus robustus from San Redondo, California. Two examples of the diatom on the slide. Prepared by WA Firth. Coverslip thickness 0.0035″ (0.09mm) which is much thinner than usual. Mounted in Styrax and dated 1892. Olympus BHB microscope using 450nm LED light. 20x Nikon Plan Apo NA 0.65 objective. Olympus Aplanat Achromat condenser, brightfield lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 14 images stacked in Zerene (Pmax).