mostly on the stamp, for me i think the fake ones usually have a deep stamping while an authentic one, though ighter is much pleasing to the eye, hahah, but in the epi i usually look at the sides/seams-- fake ones are usually obvious bec they paint it to match the epi color (side of straps) it's harder in black. i think the mandarin is the easiest to spot just bec they cant get the brightness of the orange...