American Dimes, Quarter Dollars, Half Dollars and Dollars issued upto and including 1964 are 90% silver. Coinage issued thereafter is what is known as 'Clad', basically copper and nickel layers bonded together in sheets, cut into coin blanks and then struck. They contain no silver at all. Except for the half dollars issued from 1965-1971 which were struck in copper/silver bonded layers, these contain 40% silver, after 1971 the silver was replaced by nickel. UK coinage, tiny silver threepences upto crowns issued up until 1919 were 92.5% silver, from 1920-1946 they were 50% silver, 1947 onwards they are a copper and nickel alloy. Most stuff issued after 1937 is pretty worthless unless in brand new condition (if it looks like a 2005 or 2006 penny from change then they might be worth anything upto £5 or £10 if you're lucky). If they're worn then there not worth a great deal monitarily, although they might be good to hang onto for sentimental value. There's not alot of money in post-1800 British coinage (unless they are in very high grade of preservation with no wear, no scratches and most importantly uncleaned).