We received a picture of this coin from Andy and we are duly impressed. The coin could be worth several thousands of US dollars. However, this is not the case. It is worth zero because it is a fake. Here are some observations.
Back in the old days coins minted by Great Britain rarely carried a date. You are supposed to know who is on the front of the coin, and you are also supposed to know the time period when he or she reigned. Andy's coin has Queen Anne. Here is a table of British rulers so you can tell the approximate date of your British coin:
William III, 1694-1702
George I, 1714-1727
George II, 1727-1760
George III, 1760-1820
George IV, 1820-1830
William IV, 1830-1837
Edward VII, 1901-1910
George V, 1910-1935
Edward VIII, 1936
George VI, 1936-1952
Another thing the Brits did not put on their coins was how much their coins were worth. You were supposed to know that, too. The size and the pattern made all the difference. Everyone knows, don't they, that this is a silver crown?
The small 06 on the reverse tells us Andy's coin is from 1706. A 1706 crown in uncirculated condition catalogs for $10,000 or thereabouts. I would say this is too good to be true for Andy's coin.
The second image shows a typical coin from the Queen Anne era. It is clear that Andy's coin is a counterfeit, probably from China. There are enterprising people in China, also known as crooks, who turn out copies of valuable collector coins by the thousands. Chinese fakes are setting coin collecting on its ear. If you are doing business in coins, be sure to deal only with people you trust.
In the US we have a law called the Hobby Protection Act which requires the word COPY to appear on all replicated coins. Not so in China. For Andy to be sure of his coin's authenticity, he must submit his coin to a third party authentication service. This service will ascertain if the coin is a fake or not. If it is genuine, the service will stand behind a guaranty of that fact. If Andy wants to do this, he should use one of the following services: PCGS, NGC, ANACS, ICG (look them up on the Internet). Do not use other services.