No they are not. Values depend on the denomination, date, mintmark and grade.
All coins come from a mint. Casino coins are sometimes solid silver.
Yes they do. No British decimal general circulation coin has any silver content at all. The "silver" coins of all Commonwealth countries similarly have no silver content.
Same as all other Greek silver coins: drachmas. Same as all other Greek gold coins: staters.
With those dates, the coins are Silver Eagle bullion coins that are made from one ounce of silver and value is whatever the spot price of silver is at time of sale.
These coins contain no silver and are very common. They are worth only face value. All of these coins have ridges.
It's a Eisenhower Dollar and the value is $1.00 only special collector's coins has silver. All the coins released for circulation are copper nickel.
No circulating U.S. coins were ever made of solid silver. They'd be so soft they'd wear out very quickly. All "silver" coins are part copper for hardness.
None of the bicentennial quarters made for general circulation have any silver or are worth more than face value. Only Proof and collectors coins sold from the US Mint are worth more. All the 40% silver coins do have "S" mintmarks.
The value of silver had been rising over the years and finally it was becoming close to being worth more than the coins containing it. In order to avoid minting coins that would just be melted for the silver content, the Treasury department changed the composition of all silver coins.
The worth (value $) of a silver nickel is based on the two main points as used for all coins...the amount minted in that year and the condition. Some non-silver nickels are worth more then an actual silver nickel because of low mintage and or condition. Your best bet is to just buy a coin magazine that has prices for coins from pennies to dollars.
The FACE value is the same as all other US coins set by the denomination.
1920-1966 Canadian coins have the following value as of March 2 with SIlver prices at $34.69 per ounce. Dollar: $20.81, Half $10.40, Quarter $5.20 Dime: $2.08. These are all $80% silver. In 1967 and 1968 Most Canada coins went to 50% silver. After 1968, there is no silver content. This answer is from a silver perspective only. There are rare and collectible coins that have no silver.