Hi,
I have resisted comment until now. If this is Czech, in two colours, then it is not a mainstream product. I know of very few bi-coloured Czech items in pressed glass, where the colouration is from the pressing, rather than two coloured items, being fused post-pressing. I know how this theoretically could be done. but it would have to have been a small scale manual pressing operation, where uniformity of the product was not important. Also this type of production would have required some serious pre-pressing work. So a small producer around Jablonec might be possible.
Regards,
Marcus