You will know real wagyu when you eat it. The flavor explodes in your mouth as you eat it. You can smell the beefiness of it as you cook it. You can feel the difference in your hands as you touch it.
This is all because of the unique fats of true wagyu – commonly called marbling. And it is ONLY applicable to full blood wagyu. Nothing crossbred can come close.
Here is an example of American wagyu, a cut called inside skirt steak:
Here is the same cut of beef that is full-blood Japanese wagyu:
The difference is all in the marbling. This affects how the beef cooks and more importantly how it tastes.