Those sunnies are authentic, the fonts and markings are correct and there's nothing questionable about them.
Your buyer is wrong.
I'm guessing that the buyer just doesn't like them (for whatever reason) and since you have a no-return policy, the buyer thinks he/she needs an excuse to return them.
My advice is to refer the buyer here if it's truly reassurance he/she is looking for.
If the buyer refuses, my suggestion would be to block the buyer, take the return and relist them. (The buyer got a fanastic deal! I saw those same sunnies at TJ Maxx for $60.)
albertabrightalberta
Volunteer Community Mentor