I have copied a couple of your images and am sending them out to the group working with me on the website for thoughts. I will let you know if anyone has an ID.
What about the underside? A pontil? Polished or rough ground? As far as Loetz signatures go, most is not signed, most examples that you see that are signed are not true Loetz sigs. As a matter of fact, if I see a description of a piece that says it is signed, I am almost always immediately suspicious.
Interesting piece.... I think definitely Czech/Bohemian..... The closeups do having a striking similarity in some ways to Astglas. Astglass was produced in three colors. Candia (Gold or light Amber colored), Orange, and a color referenced as dark Heliotrope, which would fall in the color range of a dark blue. I have personally never seen an example..... I have never seen an example of Astglas with aventurine/mica in it though.
I'll let you know what everyone says....