That's a beautiful mug.
Previously, such were produced here in the Czechoslovakia. They were porcelain and the transparent patterns were made with a weaker material used for the entire mug. It was called printed porcelain. When you then poured tea or coffee into it, the liquid shine through and patterns could be seen. My mom had similar but not as nice.
But my greedy sister-in-law stole everything she liked after my mother's death, so I didn't have a single one left.
But the memories are nice - when I drank from the cup, I felt like I was drinking tea from a magic cup.