COA is always Included when issued by US Mint. Issued from 1986 to date
The coins in the Pictures are a good representation of what you will receive.

1968  5 coin Proof Set.
1969  5 coin Proof Set.
1970  5 coin Proof Set.
1971  5 coin Proof Set.
1972  5 coin Proof Set.
1973  6 coin Proof Set.
1974  6 coin Proof Set.
1975  6 coin Proof Set.
1976  6 coin Proof Set.
1977  6 coin Proof Set.
1978  6 coin Proof Set.
1979  6 coin Proof Set.
1980  5 coin Proof Set.
1981  5 coin Proof Set.
1982  5 coin Proof Set.
1983  5 coin Proof Set.
1984  5 coin Proof Set.
1985  5 coin Proof Set.
1986  5 coin Proof Set.
1987  5 coin Proof Set.
1988  5 coin Proof Set.
1989  5 coin Proof Set.
1990  5 coin Proof Set.
1991  5 coin Proof Set.
1992  5 coin Proof Set.
1993  5 coin Proof Set.
1994  5 coin Proof Set.
1995  5 coin Proof Set.
1996  5 coin Proof Set.
1997  5 coin Proof Set.
1998  5 coin Proof Set.
1999  9 coin Proof Set.
2000  10 coin Proof Set.
2001  10 coin Proof Set.
2002  10 coin Proof Set.
2003  10 coin Proof Set.
2004  11 coin Proof Set.
2005  11 coin Proof Set.