Zwiebelmuster Butter Dish Bottom Part Small, Original Bohemia Blue Onion Pattern from Dubi

Painting (Onion Pattern) is under the glaze which makes the product safe to use in microwave and dishwasher. Breaking the product with a force is the only way to interrupt the painting.
(Glaze is thin, clear, and protective material applied to ceramics)

The product is very safe to use - more at http://www.zwiebelmuster.eu/zertifikat-zwiebelmuster/
In Czech Republic, There are many producers of Blue Onion Pattern, but only Bohemia Blue Pattern from Dubi using this trademark:

 
 
The trademark has been modified over the years. More you can find here: http://www.zwiebelmuster.eu/geschichte/