Paul - There was certainly only one size produced of this very popular cake plate. With many bowls etc the sizes quoted in catalogues were very nominal due to different amounts of stretching during the finishing process. With this item, however, little stretching would occur. If your example is uranium green then it is probably pre WW2. If sales then were anything like the tens of thousands which I was invoved with after the war the mould would have been re-cut more than once. Each time a small but significant increase in size would occur. The sales people probably didn't even notice!