Coins are often made of 90% silver and 10% copper, hence “coin silver”. The purity of a silver object is sometimes marked: 900 or “coin”, sterling 925, 800, or sometimes even pure silver. Coin silver is an alloy. It is harder then pure silver. Here is a website with a calculator that converts the percent of metal in an object to current spot metal value. Remember, dealers charge a commission. That’s how they make a living. So the calculation you arrive at is before the dealer’s commission.