Assuming you are referring to the new 2010 50p piece commemorating 50 years of TT Racing in the Isle of Man, this coin would be worth currently just 50p with no collector's value yet apportioned to it. Expect it to fetch £2 - £3 in 2 - 3 years' time.
Such a coin does not exist. The British 50 Pence coin was first issued in 1969.
The first British 50 New Pence coin was issued in 1969.
The first British 20 Pence coin was issued in 1982.
There was no such coin in Britain. The 50 New Pence coin was introduced in 1969.
The coin is called a "50 Pence" coin. The term "50 New Pence" was last used in 1981.
There are 50 British Pence in a British 50p coin.
Such a coin does not exist. The British 50 New Pence coin was first issued in 1969. The larger pre-1998 50 Pence coins were withdrawn from circulation and demonetised in 1998. So, unless they are part of a Proof or Uncirculated mint set or are individual Proof or Uncirculated coins and in absolute mint condition, they have little or no value.
The British 20 Pence and 50 Pence coins are both heptagons.
There are no British 50 Pence coins considered to be rare. In circulated condition, they are worth 50 Pence. For a 50 Pence coin to have any collector value associated with it, it would need to be a "proof" or "mint condition" coin in its original packaging.
A reputable coin dealer will be able to value your coin. If the coin has been circulated, you might be lucky to get 50 pence for it.
Zero. There is no silver in any British general circulation 50 Pence coin, and there has been no silver in any British general circulation coin from 1947 onwards.
Currently, British general circulation currency comes in the following denominations - 1 Penny coin 2 Pence coin 5 Pence coin 10 Pence coin 20 Pence coin 50 Pence coin 1 Pound coin 2 Pound coin 5 Pound note 10 Pound note 20 Pound note 50 Pound note