It is a bullion coin minted by a private mint. It's value is determined mostly by market price for silver.
On the reverse above the D in Dollar.
1879 would make it a Morgan dollar, which has an eagle on the reverse.
Mintmarks are on the reverse above the letters DO in dollar
Feathers, that are on the EAGLE that is on the reverse of all US silver dollars
There is no 1921 barber silver dollar, it is either a peace dollar (eagle perched on a rock engraved PEACE on the reverse) or a Morgan dollar (Eagle with gothic lettering above it saying "In God we Trust" on the reverse)
On the reverse of the bicentennial silver dollar is the Liberty Bell super-imposed over and image of the moon.
By the mint mark on the reverse of the coin, but silver dollar coins with no mint mark are made in Philadelphia
If it has one, it's on the reverse above the DO in DOLLAR.
If it has one, it is on the reverse just above DO in DOLLAR.
On the reverse side between the letters and the eagle
Mintmarks are on the reverse above the letters DO in dollar
If it has one, it's on the reverse above DO in the word dollar.