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Hi Andrew
It might be Richardson, but I suspect it belongs to the OE1 Group that I have written about. If you were able to measure the Specific Gravity that would distinguish between the two: nearly all Richardson pieces are in the 3.11 to 3.15 range, whereas the OE1 are lower at 2.88 to 2.93.
Images of a couple of OE1 Group pieces below.
Alan