In Reply to: What happened in 1969 that made the mint print so many versions of bills?...(m) posted by KsherHomey on March 14, 2003 at 3:15 PM:
During Series 1969 and prior, the series number usually changed only when the bill was redesigned. Changes in signatures only was designated by a letter following the year. The various 1969 series all had the same design with different signature combinations. The difference between 1963 series and 1969 series was changing the treasury seal from Latin to English. For example, Series 1963B was created 12/1969! Series 1969D was in place into 1974. Go to the link below for more information.