Hi Leni,
I am afraid that probably the only people that could say for sure, are the people who made/make the glass.
Once the label comes off, then I think, even experts have trouble telling items apart. Sure there are certain clues, but the very nature of off-hand art glass such as are being discussed in this thread, means no indicator can be other than an indicator, and certainly an indicator cannot be a guarantee of identification. However, the majority of Chalet is drawn or pulled, where Czech, appears to be a roughly 50-50 mix of blown and drawn. Added to that is the export of glass from the countries involved, Italy Canada and CZ, then you have a real problem.
Colour does help, but not always. Form can help, but many forms are replicated in all producing countries.
Even when you have catalogues, I doubt anyone can be certain, and probably the safest way would be to say: "Possibly..Chalet, Murano, Czech....."
Regards,
Marcus