Spirou Pirates is a bootleg Spirou adventure, an unapproved fan comic by “Sergueï & Mikäelof” (pseudonyms), printed in a few different limited editions in 1999. Some of those editions include ex libris prints (prints on loose cards inserted into the book), and this looks to be one of them.
The comic itself was mostly copied from panels by Franquin (as well as various other artists), edited in various ways to tell a new story. It used to be available online at http://spirates.ifrance.com/, but the server has been down now for years. However, you can find it here, and there’s also an English scanlation on a certain site that offers that kind of thing.