The coin necklace is just the perfect gift to give to your spouse or partner. The necklace is a unique gift, and I think it should be perfectly appropriate for this particular occasion.
This one is a bit tricky. As an anniversary gift it is a pretty standard, but what I would recommend is an updated version of the gold coin necklace. These are usually made out of real gold or platinum, and are made in a way that allows the wearer to see any detail of the design on the necklace. The new version of the gold coin necklace is designed to be more subtle, and to show off even more detail.
