What a beautiful plate - congratulations, Claudio! I am sorry that I have not been able to reply sooner, but I've been away for a few days and have only just had the chance to study this beautiful item.
The pattern is known as "Daisy and Scroll" and it is currently reported in the shapes of decanter and shot glass, in both blue and marigold. All examples that I am aware of have been found in South America - however a Daisy and Scroll decanter, shot glass and tray are illustrated in the Hortensja catalogues (Poland). There are some differences between the Hortensja illustrations and the Carnival items that have been reported.
The circumstantial evidence currently points to the Daisy and Scroll Carnival items being made in South America (Argentina or possibly Brazil). Carnival from Poland is not known in blue - but Carnival from S. America most certainly is known in blue. That observation, coupled with the location of all currently reported "finds" that I am aware of, plus the differences in the Hortensja catalogue illustrations, lead me to believe that this lovely plate (and the other known Carnival shapes in the pattern) was made in South America.
This is the first plate reported in the "Daisy and Scroll" pattern. It's magnificent. Again, congratulations - and thank you for showing us this rare beauty.