The Bill of Rights was an important Act of the Parliament of England. It limited powers of the king, defined the rights of the Parliament and laid down rules for the free speech and election requirements of the Parliament. It included other interesting provisions. For example, the Parliament's consent was now required to maintain a standing army in times of peace.
The UK chose to commemorate the 300-year anniversary of the Act by issuing £2 coins. A similar Act was passed in Scotland in 1689 known as the Claim of Right Act, and the Scottish versions of these two pound coins name this Act instead of the Bill of Rights. The Scottish coins also portray the Scottish Crown instead of St. Edward's Crown.
The 'squiggly lines' are the royal cypher or monogram of William and Mary, the ruling pair of regents when the Act was passed. The monogram is shown on top of the mace of the House of Commons.
There is a good write-up on these coins over at Chard, and CoinQuest thanks them for use of their coin image.
Values for these coins depends on which version you have:
- Piedfort Silver Proof, 0.9505 ounces silver
- Silver Proof, 0.4752 ounces silver
- Specimen, no precious metal content
Proof coins are made solely for collectors and do not enter circulation. The Piedfort proof is extra thick, giving it extra silver content. Proof coins are worth their weight in precious metal. If, for instance, you have a silver proof with 0.4752 ounces of silver, and if silver is selling for, say, $15 US dollars per ounce, the value of your coin is 0.4752 x 15 = $7. A collector would probably pay double that amount if the coin is in perfect condition, but a dealer would only pay silver value to buy it from you. Gold coins, of course, are very valuable due to the price of gold.
Specimen coins (not proof) are worth face value - two UK pounds, currently equal to about $3.25 US dollars. Use a website such as Xe.com to convert between currencies.
Some specimens are found sealed inside the original packaging from the mint. An interested collector may buy a packaged coin for $10 or so.