One more 2 cents worth: 1. You sold the freewheel in good faith. 2. You are not a merchant. 3. You are not bound by the errors of the manufacturer or original retailler. 4. Buyer (claims) took freewheel apart. a. this in itself voids any recourse 5. Return is not apprpriate because the part has been "tampered" with. If the buyer sought to return before "opening" the freewheel he might have a cause. 6. buyer did not say there was any defect except missing balls; did the mechanic replace them, if so why not. 7. If a shop mechanic were involved was he competent to work on an open ball freewheel? I come across young mechanics who know nothing about anything made older than 2 or 3 years ago. I have had some categorically state no such thing ever existed as what I am talking about. For instance metal stemmed and threaded schrader valve tube stems. I still have several Hutchinson tubes of that style. Others have never seen a thorn remover that is a wire mounted to the brake bolt by clear plastic tubing that rides on the tire to pull out thorns. They deny that is what it is when shown one and argue it is no such thing. 8. buyer claims no error in description.
When you sell an item in good faith, that is it. If the item in fact is defective but unaltered there is the possibility for a return at your discretion. The freewheel is no longer NOS, it is now used. In effect any , although wrongly perceived fitness for use no longer applies.
I would refer buyer to the Universal Commercial Code (UCC). I would tell him I am sorry but by his own admission he has tampered with the item and it can no longer be returned.
I know there are bad sellers. there are also bad buyers. You can wait and see or I suppose lodge a complaint that he has supposedly opened the freewheel (ie altered the condition) and there is no assurance it is in the same condition as sent and is thus not returnable. Any return would have required return as received.
I am not defending you or being derisive of the integrity of the buyer. I would not take a return after the item is claimed suspect and then not returned in conditin received unless defective on its face.
Mostly It is up to you. I would not accept it back. the spectre of buyers remorse is all too present.
Blah, blah, blah! Move on.
John Strizek
sacramento california
in the USA