I gave my diamond ring to a jewler to sell. I have bought and sold Jewlery to him prevously.He paid me cash and had me sign papers verfying this was my jewlery also took my thumb print.He never gave me a reciept just the cash. He had never given any reciepts prevously. He called me several hours later very nicely to say he took apart the ring and that the center stone wasnt as big as he thought. So he wants his cash back.He had this ring for several weeks and hes the Jewler, not me. This transation was all in good faith. He made an offer 1500. lower then my asking price and I finally agreed to sell. Now hes not happy with the purchase. What is my obligation under the Law?