1968 silver half dollar

No.

In the 20th century the U.S. minted true silver dollars (i.e. made of 90% silver) from 1901 to 1904 and again from 1921 to 1935. A trial run of new dollars was made in 1964 but they were never released and all are presumed to have been melted.

By 1965 the price of silver had increased to the point where silver coins were worth more than their face value so not only was dollar production again suspended, new lower-denomination coins were struck in cupronickel instead of silver. From 1971 to 1978 a large-size (38.1 mm) cupronickel dollar coin was minted but it only circulated in a few regions of the country. In 1979 the coin was downsized to 26.5 mm, and in 2000 the metal was changed to the gold-colored brass that's used in the current Sacajawea and Presidential dollar coins.