Chribska production cannot ever be described as Sklo Union. Formerly the oldest glassworks continuously in production anywhere in Europe, they have only made off-hand glass, and never, as far as I am aware, pressed glass.
The business was established in the 15th century, before pressing of glass became an established part (19th century) of modern industrial mass-production.
Czech glass had an unrivalled purity in the late 18th and 19th centuries, which is why much ordinary sodium-potash glass has been referred to as crystal, without any lead additive.
I'll take Czech glass most times, and who knows, your Murano piece with label, may still have been made elsewhere, like a recent suit purchase, labelled visibly, Made in Italy, in the pockets.... Fabricado em Portugal
Don't you just love globalisation, and out-sourcing?? NOT!!!