Unknown stoneware

This cup is mainly on the lighter side... (right side of photograph). The lava glaze has puddled around the footrim, which is similar to Japanese style tea bowls. It's about 10% too large for most tea bowls I've seen, but the shiny interior is good for tea.
It's not as thinly potted as Natzler, but is equally beautiful. The mystery is driving me crazy, since the piece was sitting between a Natzler bowl and a Pillin vase at a local estate sale. (My friend beat me to the Natzler, which was a real steal!)
The exterior glaze is about the color of oatmeal, with a bit of volcanic lave texture thrown in.
Thanks for any guesses about it!
Fran E

