This is a bullion coin containing 1 troy oz. of gold; the $50 denomination is artificial.
Precious-metal prices change every day so any specific answer posted here would be out of date almost immediately. While it's not Answers.com policy to say "use the internet", that's the best approach in this case. You can check a site such as kitco.com, CNNMoney, etc. for the latest spot price of gold, then add a couple of percent to account for the fact that the Maple Leaf is a proof coin with the added imprimatur of being issued by a major government.
Whether it's a US Anthony dollar or a Canadian "loonie", it's only worth face value.
The value of an 1879 Canadian dollar depends on its condition. Such a coin in good condition is valued at about 24.82 US dollars while an uncirculated coin is valued at 42.88 US dollars.
The coin is still in circulation and only a dollar.
The coin is a 1979 SBA dollar and it's NOT silver. The coin is still found in circulation and is just a dollar.
The 1979-D Susan B. Anthony dollar is still in circulation today, the coin is face value.
One dollar.
about $10
The coin is not a silver liberty dollar. It's a 1979 Susan B. Anthony Dollar coin and has no silver in it and the value is one dollar.
With the date of 1979 the coin is a Kennedy half dollar, it's worth 50 cents.
Without further details, the best possible answer is that it's worth one dollar.
The 1979 SBA dollar coin is still in circulation today, value is one dollar.
$2