In 1985 the Royal Mint issued its third Pound coin and, for collectors, they also issued them in Proof Sterling Silver. It was part of a four coin series to honour the different parts of the United Kingdom. In this case the 1985 issue had a leek for Wales on it and in this same year the Royal Mint also changed the portrait of Her Majesty on our coinage from the Machin bust to the so-called Maklouf bust engraved by Raphael Maklouf.
So you have the first year of a new portrait of the Queen and you have it on a Sterling Silver Proof example of the One Pound coin.
They are in Choice Proof FDC condition in a capsule and struck in Sterling Silver, add one to your collection, there are not as many around as there once were.