Aside from the ?18A? mark, are there any impressed or quietly etched marks anywhere on the piece? Sometimes the glaze can hide a cipher, so give it a really good going over. After that, you are on a prayer, because you'll have to research the glaze style and there are no end to the similarities between potters and variations of style displayed by any single ceramicist over the course of their career.
On second look, is there a mark incised in the middle of the foot? It's hard to tell. If you can give any hints what that reads or looks like better than we have here, you may have a starting point.
