The "Etoile d'Or" as Anne says, gold star, was the highest award by the judges, of the Brussels World Exhibition in 1958. The medal given to the exhibition design team of the Czech pavilion features in the book, and is exactly the same pattern as your label. It is not unusual for companies to issue labels denoting their success, (Arzberg fired commemorative marks of thier designer's (Loffelhardt) double ceramics success at the 1957 Milan triennale) but etching such on glass would have been difficult, and labels had to suffice.
This is a silver label, but as yet I have not identified whether it was used by Jablonecke Sklo or Jablonexport generally on a lot of items, or solely on this particular pattern. That they (the labels) are not common, is an indicator that they went on that line of product only, suggesting that the designer won an "etoile d'argent".
With your permission, I will post a link to your image, to a friend in the Czech Republic, and ask if he has knowledge of Konak, Platek or Hanus, ever winning an award in Brussels.