Interesting slide this one. It is labelled Stictodiscus buryanus (I am not convinced by this and will explain more in a minute). Single example on the slide. There is a label which says ‘8t5’. No idea on what that means. No makers name. Olympus BHB microscope using 450nm LED light. 40x Leitz Pl Apo NA 1.00 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 34 images stacked in Zerene (Pmax).
I don’t actually think this is Stictodiscus buryanus. I’ve seen a few more of these types of diatoms now. I think this could be Stictodiscus johnsonianus (Schmidt’s Atlas, Plate 443, Figure 1). It’s the dot patterning that makes me think this. Towards the rim, the dots go into groups of 2 or 3 for S. buryanus, but with S. johnsonianus, they remain (predominantly) singular. Also, maybe Stictodiscus truani (Schmidt’s Atlas, Plate 446, Figure 3). Example of both of these can be found on this site. Again, this looks similar. Is it a Stictodiscus? Yes. Is it S. buryanus? I think not. However I have been wrong before, so will leave it open for now.
I’m not sure on the maker for this, but I have just imaged a few of them which I think are by the same maker, and they are all interesting slides. If you want to see others by this maker search for BBBBB in the search function.
EDIT – based on the handwriting and style, and some conversations with experts, I this could be by Edmund Grove (of Grove and Sturt). But I have no 100% proof of this at the moment.