I finally found pictures showing my Skrdlovice Topaz- Amethyst. Not cased sommerso style with two colours. It is a single colour as you would expect with similar Jelinek patterns (but it is a bit of a one off really, 5.5KG). In normal light away form direct sun it is a smoky brown colour that can look near opaque. I show a picture of it lit with a lightbulb set up to make it clearer. But in some daylight, it quite often turns Amethyst. I do not know why, or if this was hard to achieve! Maybe it is linked to it being a strange size too....
Robert (bOBA)