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I can't really help on origin, I'm afraid - some of these are Chinese, some are not. But the 'control' on the bubbles will always look good on these designs, because the bubbles arise from pressing the gather of glass into a 'pineapple' mould that makes lots of little regular indentations. When these are covered with another layer of glass, you get a tiny bubble at each indentation - all in very regular positions. No real magic or special skill involved, I'm sorry to say.
Alan