The Disintegrating Necklace is exactly what it means, it’s a necklace, and, after a period of time, it disintegrates, just to go back to the place where you picked it up. It’s exactly in every way a gold and diamond necklace, but if you sell it for the 1,000 gold the real one is worth before it disintegrates, you just won yourself a fairly large profit.
The Merchant of Kintro wanted to have a little villainous fun with his customers, making a necklace that would disintegrate within a couple hours, to make a few coins. He would then blame the disintegration on the customer, and refuse to refund the money. He took his idea to a wizard, who liked this idea. He made the item, and then thought he would have some mischief fun himself. He duplicated the necklace and placed them all over the land, and they could be anywhere. On a shelf, on the ground, anywhere.
Once the necklace has contact with a lifeform, it has two hours until complete disintegration. Run it to the merchant as fast as you can!