Otto Grunert Kahla porcelain lusterware bowls ?

I can't find this mark anywhere. It's a set of six little bowls. The mark underneath is "OG" in a circle, with the name Germany, and number 136. Is anyone familiar with this?

Edit: The OG was the back stamp used by Otto Grunert, a Porcelain & Chinaware dealer / exporter from Eisenberg, Thuringia, Germany.