No such thing as a 'mint stamp' in dealing with coins. They are called "Mintmarks" for Morgans, all are on the reverse of the coins. The easy thing to do to see one is, in your search box type in Morgan dollar mintmarks and click on images.
This link shows a 1879 Morgan Dollar: http://www.coinfacts.com/silver_dollars/morgan_dollars/1879_morgan_dollars/1879_morgan_dollar_obv.jpg
Bolender shows a large number of varieties. There's more information at the Related Link.
The 1890-S Morgan dollar is a common coin and circulated examples have retail values of $23.00 to $40.00 depending on how much wear the coin shows.
Assuming the coin is circulated and has no mintmarks, current retail value is $33.00-$44.00 depending on how much wear the coin shows. The 1888 Morgan dollar is very common.
The last Morgan dollars were minted in 1921. The Peace design was introduced in December of that year, so any silver $1 coin dated 1922 would be a Peace dollar, just as it says on the coin's back side. The last Morgan silver dollars were minted in 1921. Your coin is called a Peace dollar. A 1922 peace dollar that was made at Philadelphia in circulated condition is worth an average of $25. This reflects the silver content. If it shows significant wear it won't be worth much more than that. If it is uncirculated they are worth up to $900 depending on quality.
PCGS shows a retail price of about $1300, although that may be a bit on the high side.
The coins were issued for different purposes and have different designs. The Trade dollar was slightly heavier and issued only for Overseas circulation, mainly in the Orient. It had a Liberty figure seated on the front (the joke was on a toilet seat) while the reverse has a heraldic eagle. (Oddly the positions of the olive branch and arrows in the eagle's talons are reversed, signifying a preference for war. The Morgan dollar is only one of a series of silver dollars that were minted for use in the US. "Morgan" refers to its designer, George T. Morgan, rather than to the denomination as a whole. Other silver-dollar designs included Liberty Head, Peace, Seated Liberty, etc. Morgan's design shows stylized Goddess of Liberty with a visored crown, and seems to be based on the Greek goddess Arethusa - a maritime goddess- maybe the princess of Atlantis, so to speak, while the tails side shows a spread-winged American eagle. Both Latin and Gothic letterings are used on the reverse of the Morgan dollar.
Assuming the coin is circulated and has no mintmarks, retail value is $23.00-$31.00 depending on how much wear the coin shows. The 1890 Morgan is a common date.
Assuming the coin is circulated and has no mintmarks, retail value is $23.00-$31.00 depending on how much wear the coin shows. The 1890 Morgan is a common date.
Assuming the coin is circulated and has no mintmarks, retail value is $26.00-$32.00 depending on how much wear the coin shows. The 1882 Morgan is a common date.
Assuming the coin is circulated and has no mintmarks, retail value is $32.00-$44.00 depending on how much wear the coin shows. The 1890 Morgan is a common date.
Assuming the coin is circulated and has no mintmarks, retail value is $32.00-$44.00 depending on how much wear the coin shows. The 1890 Morgan is a common date.