Set of four unmarked stoneware mugs, 1970s vintage, nice and heavy with a matte finish glaze. These look like OMC or Otagiri Japan to me, but I haven't been able to track down this pattern name, or even the maker for certain.
They're about 3 1/2" tall overall. All four cups are in excellent condition, no damage or noticeable wear. A great set, so retro!