The gestation period for an elephant is 640 to 660 days. This is equivalent to about 95 weeks, or 22 months, and is the longest gestation period of any mammal.
Dimes dated after 1964 are copper-nickel clad and contain no silver. Quarters are also clad, except for the bicentennial commemorative coins with an S mint mark that were produced for mint and proof sets. Kennedy half dollars from 1965 to 1970 were 40 percent silver composition. After 1970, all Kennedy halves were clad, except the same S bicentennial issue.
A Brief History of The US Silver Half Dollar. The production of silver half dollars in the United States started in the early 1790s. These pieces have a face value of $0.50; however, depending on the year the coin was minted, it may be worth much more than this. From 1790 to 1965 every single coin in the mint was made with 90% pure silver. From 1965 to 1970, this dropped to 40% silver. However, since 1970 the coins have been made without silver. The coins were particularly popular in the first half of the 20th century.