The crown is also known as the five shilling piece. Today, this would be an insignificant 25 pence, although the Royal Mint continues to produce coins that are crown sized. The Crown follows the silver weight. There are about 110 grams of weight in a sterling pound, so a Crown weighs about 28 grams. This would be sterling silver before 1920 (92.5 % silver, and 50% between 1920 & 1946).
Just to confuse matters, the Royal Mint now produce a £5 (five pound) commemorative coin with the same size and dimensions as the old crown. They must be mad!
More tomorrow, including some pictures!