It's not as thick walled as the Czech glass pieces though
I know what you mean about the thickness and chunkiness of much Czech glass generally, but I wouldn't say the example I posted was particularly thick and looked much like mine in terms of thickness.
Anyway, I've found a page, through a link on the page I posted, to the Skrdlovice pattern book and there are further ringed bowls, so I'll see if I can find a shape and dimensions match. I'm still disinclined to think it's Czech because the colour and polished pontil isn't something I associate with Skrdlovice, but you never know ...!
Cheers Geraint.