There have been rumours circulating in the UK that the �2 coin where the Queen is wearing a necklace is worth a lot (the highest figure quoted is �75). There have even been rumours that they are being recalled and that banks and post offices will give a premium for them.
This is an urban legend.
Banks and post offices will only give you �2 for them. No fewer than 13,734,625 have been issued for circulation, according to the Royal Mint.
There was a problem in the production of the new bimetallic �2 coins which meant that the release date was delayed from 1997 to 1998. In the meantime the portrait was changed for the newer coins minted in 1998. They issued the 1997 coins (with the 'necklace') anyway, in large quantities.
They are not worth more than �2, nor will they be unless in uncirculated condition in a lot of years time (as will the 1998, 1999, etc coins)
On the other hand the Guernsey version of the coin dated 1997 is scarce as it was only issued in the Guernsey uncirculated coin sets (as you may know both Jersey and Guernsey issue their own coins).