This is a vintage Art Deco blue glass bowl, likely from the Hermanova Huť glassworks, which was founded by Carl Stölzle.

These bowls were designed and made in the 1930s in Czechoslovakia.
The bowl is made of pressed, thick glass and is characterized by its distinctive shell pattern and footed base.

The Hermanova Huť glassworks was a well-known Bohemian glassmaker.
The style is often sought after by collectors of Art Deco glassware.