Cartamundi uses a technique known as offset printing to print magic cards. This process is also the reason for the rosette pattern and further described on this page. For solid black objects they use an additional black layer to get these objects crisp and sharp. This technique is called CMYK+100%K (K being “key” or just black) or overprinting. If you are interested in how it works, this website describes it quite well.
Overprinting requires a printer setup which even a lot of “professional” counterfeit operations don’t have. It requires five, not just four printer units in the process and a proper pre-press process. But printing machines are expensive. A fifth printer unit is nothing every shop has by default.
Below are some pictures of a chinese counterfeit with rosette and additional key layer and a closeup from an american fake without the correct key layer. As always, checking the details can just make you spot differences, some things might match, others might not.
A Word on Chinese Mass-Production Fakes
Interesting enough is that a lot of the asian counterfeits seem to have these ressources and can reproduce this already. This shows that these counterfeits are done by real printing companies and not just small shops. They redo the entire card and produce very well done fronts. Still they are unable to do good backs and proper coloring. Their cards are mostly too yellowish and sometimes even really badly off. I assume since they check the color with the wrong light in the shop and lack of correct color settings (RGB/CMYK?) during pre-press. But for the black lines and textboxes we are discussing here they are close to perfect. That is just the result of the professional ressources used.