While the provided search context titles are relevant, the text itself does not contain the specific compositional data needed to answer the question. Drawing upon established numismatic knowledge, the silver content of a Seated Liberty half dollar varied over its long production history due to legislative changes in the coin's standard weight.
Throughout its entire mintage from 1839 to 1891, the Seated Liberty half dollar maintained a composition of 90% silver and 10% copper. However, the total weight of the coin, and therefore its actual silver weight (ASW), was adjusted on two separate occasions.
From 1839 until early 1853, the coins were minted with a total weight of 13.36 grams. Based on the 90% silver composition, these earlier issues contain approximately 12.02 grams, or about 0.3866 troy ounces, of pure silver.
In 1853, the Coinage Act reduced the weight of silver coinage to prevent it from being melted down for its bullion value, which had exceeded its face value. From 1853 to 1873, Seated Liberty half dollars weighed 12.44 grams. This resulted in a lower actual silver weight of approximately 11.20 grams, or about 0.36 troy ounces. These coins are distinguished by arrows placed on either side of the date.
A final adjustment was made with the Coinage Act of 1873, which slightly increased the standard weight to 12.50 grams to align with metric standards. Coins minted from 1873 until the series ended in 1891 contain approximately 11.25 grams, or 0.3617 troy ounces, of pure silver.
