I'll take a positive / hopeful view of these. If I get to venture a guess then the subject material (muses), the shape of the bottom, the depth of the number impressions, the paint smears at the edge of the bottom looks fairly similar to that of Royal Bayreuth Tapestry products. If my eyes see correctly what you refer to as the stamp of the rising sun may not be a maker's mark at all, but rather in importer's ID so he can comply with import requirements. Below the glaze there is no mark, so if imported something would have had to be added, hence the mark you can't find anywhere. That rising sun mark looks to be above the glaze. I haven't had time to do a comparison of the art transfer to RB's but I Iooked at a couple of my pcs. and I'd say it merits investigating. Very hard to make such judgements from photos and at best it's just a guess on my part, but a try at helping. Take a look at currently displayed item 314886427908 and you can get somewhat of an idea of what I mean. The shape is similar as well. Hope that helps.
