It looks like the blue was blown into a dip mould (internally serrated, or cog-like) caste iron mould to get the ribbing, then after more working the opaque white trailing would have been added to the outside surface - probably by eye/hand - although there are also ways of doing this by machine.
The top rim appears to be fire polished (rounded from heat) and the base pontil is ground and polished with the surrounding base area flatted, but that appears to have no wear. This doesn't always mean that the piece is young or new, but I'm guessing in this case it may be.
Difficult, because you've no idea of provenance when you buy from a boot fair in particular - unless you can build up a good repore with the seller and can then feel you trust whatever they tell you about it's past. I still feel this is probably very young.
Oh, the best introductory book on Czech glass generally is probably Mark Hill's "Hi Sklo Lo Sklo", but if you want to understand all about much Czech pressed and mould blown glass you should buy "Sklo Union, Art Before Industry: 20th Century Pressed Glass" by Marcus Newhall - both are members of this board, and both books are available through the internet (ebay and Amazon respectively). They would be a good investment if you are going to collect Czech glass from the post-war era.