Japanese china snack set

Set of Japanese china snack set.  Set of 6 plates, 6 cups.  No chips, scratches, cracks, or staining.  These are absolutely perfect.  The china is so thin on the cups, you can see your finger on the other side.  The inside of the cup looks like lusterware.  The stamp on the back says Made In Japan, not Made In Occupied Japan.  So these are either really old, or just vintage.  I haven't been able to find ANYTHING even resembling these on the internet.  I heard these may have been trade items, but I have no idea what that means.  I got them at an Estate Sale of a woman who owned an antique store.  The stuff she had in her house, according to her daughters, was the stuff she wasn't willing to sell in her store.  So that means they're either really valuable, or she just thought they were pretty.  I have no idea.  Any info you can provide on these would be soooo appreciated.  HELP!!!!!!!!