New Chanel sunglasses feature a serial number etched into the right lens. The code consists letters and numbers with no spaces between the characters. Check that the etching is clear and straight. Older models might not feature this code.
The inside of the left temple features a model number followed by a colour code and frame measurement. The model number is usually 4 digit followed by a letter indicating the arm detailing. The colour number is preceded by a lower case 'c' then usually 3-4 digits followed by 1-2 more digits and/or letters. The Chanel logo may also feature on this temple.
The inside of the right arm usually features 'Made in Italy' followed by a letter then the letters 'CE' signifying European Conformity. The Chanel logo is also often featured. Check for any errors in spacing or alignment.