Courtesy of BP/Sophie:
Updated Version
8-digits----
12XXXXXX series - 2008
11XXXXXX series - 2006 to 2008
10XXXXXX series - 2005 to 2006
7-digits--
9XXXXXX series - 2004 to 2005
8XXXXXX series - 2003 to 2004
7XXXXXX series - 2002 to 2003
6XXXXXX series - 2000 to 2002
5XXXXXX series - 1997 to 1999
4XXXXXX series - 1995 to 1997
3XXXXXX series - 1994 to 1995
2XXXXXX series - 1991 to 1994
1XXXXXX series - 1989 to 1991
0XXXXXX series - 1986 to 1988
Early 0XXXXXX series hologram stickers (1XXXXX to 2XXXXX) did not include the '0' on the stickers; thus, they contain a 6 digit serial number. But the authenticity cards include the '0' in front of the serial number, making it 7-digit.