General measures to spot fake Chanel sunglasses
1) If you see Chanel tags hanging on the sunglasses, they are absolutely fake, as shown below:
2) Beware of obvious fake Chanel sunglasses case:
Some examples of genuine Chanel sunglasses case:
3) If you see these tags or authenticity tags, they are likely to be fake:
The tags (at the back) are longer than usual. Original ones are supposed to be half the size and they should open nicely as a booklet, as shown below:

