it looks many like loetz marker. but in glas then dont know if they did ceramics.

The end of World War I brought with it the end of the Austro-Hungarian Empire, and as a result, Klostermühle found itself within the fledgling Czechoslovak democracy. Loetz marks after this date no longer have the word Austria – when the country is named, it is Czecho-Slovakia the last mark is one of my own on a smoked cristal decanter