I had an experiance recently,like to share,
I purchased a 22k gold chain on may 2009 from Atlas jewellers doha, since it is cut by my kid, i went to exchange to another gold shop ,after testing my old chain,they said it is only 21K, and it can be valued 6 QR less than current market price.
then i went to atlas and exchanged, they have valued 4 QR less than the market price and reduced about 1 gram in total wt as loss.