This coin is a Top 100 Morgan Silver Dollar 1882 O over S VAM 4 variety. The reverse has a very nice tone.
The variety shows an O over S with the center of the S recessed within the O.
What are TOP 100 Morgan Dollar VAMs?
In 1996 Dr. Michael Fey and Jeff Oxman published the TOP 100 Morgan dollar varieties with the intention to focus collectors and dealers on the most extravagant VAMs known. The identification of the TOP 100 VAM list has moved many of them into the mainstream collecting of Morgan Dollars. Many collectors regard many of the TOP 100 VAMs as a must to complete a Morgan Dollar collection such as the 1882 O/S, 1900 O/CC, Hot Lips, and Scarface varieties. The TOP 100 varieties are also certified by the major grading companies which allow collectors to amass complete registry sets for the TOP 100.