Factors that influence the price of a 1921 Morgan silver dollar are the mintmark, quality of preservation and current silver bullion prices. The price a collector is willing to pay depends on his reason for collecting.
For those collectors primarily interested in the silver content of the coin, the price is tied to current silver bullion prices. For numismatic collectors, the key driver of price is the quality of preservation or the grade. Uncirculated coins with high luster, no wear, few abrasions and eye appeal bring the highest price.
The 1921 Morgan silver dollar was minted in one of three locations, and each is collected and valued separately. The coin minted in Philadelphia carries no mint mark. The coin minted in Denver carries a "D" mintmark, and the coin minted in San Francisco carries an "S" mintmark.