If you refer to British general circulation Threepences, there are no rare coins.
There were 5.578 million 1933 British 50% silver Threepences minted. They are not especially valuable or rare. If you have doubts about the authenticity of your coin, take it to a reputable coin dealer for a positive identification.
1890 is a common date Morgan and is not rare or scarce.
It would depend on the coin! They made many silver George V coins in 1929. It could be anywhere from a silver crown to a small penny.
They are a relatively rare coin, very few were ever minted.
1961 is not a rare date for Washington quarters. If it has any wear, the value is about $5.00 just for the silver.
George T. Morgan never designed a circulating half dollar. He's known for having designed the famous silver dollar(1878-1904 and 1921) that carries his name.
1957 is not a rare date for Washington quarters. Its value is based on the silver it contains -- as of 12/2008, about $2.50
Most silver US quarters are not rare or even scarce, but it depends on the DATE of the coin, post new question.
It is worth about $1.20 in silver scrap if circulated and up to $5-10 if uncirculated. It isn't a rare date and is 50% silver.
1942 is not a rare date for Mercury dimes. In circulated condition, it has about 75 cents worth of silver in it. A nice uncirculated one is worth about $5
It is not rare, just expensive. But, you can get small silver coins for as little as $2.
A rare Morgan Silver Dollar is 1876.