Thanks, Paul, great pics. The Richardson lenses perhaps seem (from the photos) more strongly defined and certainly smaller. Sitting here with the bowl on the table next to me, the similarity between the bottom Webb bowl and the one I have is striking, both in terms of colour and lens configuration, with horizontal ovals at the top and vertical ovals at the bottom, as well as their size and even number of rows. Finally the Richardson rim is of an even thickness while the Webb is slightly undulating. Impossible to be emphatic based on the evidence of a few examples, of course, but the attribution seems a little less uncertain than when I first enquired. I'm very grateful for the contributions.