You must be the 15th correct answer (I'm sure I was the first again! I hate this method! ;) )!
All you have to do is to register at the online store (this can be a downside for non-portuguese users) and answer the question "What is the year of the Royal Battle between Portugal and Castille?" The concept of "battle royal" may be different from the translation to Portuguese, I found it close enough but I am not sure. The original in Portuguese is "Batalha Real".
Anyway, it is a tricky question, but I will give a hint... like nowadays, early Spanish loved August in Portugal!
Second giveaway, click here: