This beautiful little jug (sadly not one of mine) has a lovely mark underneath that shows the design has been Patented by the manufacturer. Why would anyone apply for a patent for a jug - they've been around for millenia, you say. The Patent would not be for the shape of the vessel, or even the pattern design (that's what the design registration diamonds and numbers were for). Patents were taken out on new innovations such as a new type of glaze, or design function (such as a self-closing lid). In this instance, the Patent was taken out by Powell Bishop & Stonier for their new Ivory Porcelain. This is intriguing as it may be that this was the beginnings of the the Oriental Ivory range of earthenware. Further investigation may be needed i suspect to find out whether this new Ivory Porcelain continued in production under that name, or whether it did indeed morph into the Oriental Ivory that is now familiar.