There is no potter shape name for this shape but there are two collector names.  We have even seen it called Gothic Octagon.  The plain version of this shape was registered June 8, 1883.  On February 12, 1884 the embossed Prunus Blossom (Cherry Blossom) was registered.  The shapes are identical with the exception of the embossing of the Prunus Blossom.  More often than not, the pieces (embossed and unembossed) are marked with both the impressed diamond mark for June 8, 1883 AND the printed square with the date February 12, 1884.