On looking at everything again, I've come round to Anik's point of view, that the piece is indeed 7603. The pattern 7603 is shown with all the lines running vertically or horizontally. When I looked at the pieces I have from that series, none of them quite achieve the same consistency of the markings being either vertical or horizontal. Yet the alternative, 8225, is far more organic and on the diagonal. So, I'd lean towards a confident attribution of 7603. Congratulations on a great piece, again.