Thanks, Nickie and UkeMania!
It's an Ukumele acacia soprano. (No typo, the name is "Ukumele", really. It's from a German vendor, and it's called "ukuMele Akazie Sopran" in German.)
Acacia is not too different from Koa, and it's a really good wood for ukuleles IMHO.
Best Regards
Wilfried