I just read another of that seller's guides. He/she is either totally naive or is lying through his/her teeth. He/she says:

"all of our jewellery is either stamped the following stamps which are International Stamp of authenticity

stating the carat of the metal used in making these items of jewellery if you buy a item which hasnt been stamped then
there's a good chance its not real .

Please make sure your seller states that the jewellery is stamped as mentioned its a stamp of authenticity."

"Stamp of authenticity' - my fat aunt!!  There are THOUSANDS chains  stamped "925" or "925 Italy" and they are ALL FAKE.

On another point, it says "is either stamped ...." {or what} ?????