Here's the mark : There are numerous fine white lines on real Ajwa dates on one of its sides, as shown in the picture above. That's the differentiating element between real Ajwa dates vs the fake ones. Real Ajwa dates have these white fine lines at the bottom. On one side. The other dates don't. White lines which look like as if the date has cracked due to dryness. Even thought it might not be actually dry.
Also look for mixed bag. In a single sack some dates might be Ajwa, while others not.
This is the big difference. And the main one.