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.
From 1837 through 1964 the silver percentage was 90%. From 1965 through 1970 half dollars and silver (Eisenhower) dollars were made with a core of 21% silver, clad with an outer layer made from 80% silver. From 1971 through the present the US Mint has produced no coins for circulation that contain any silver.