TYPE ZERO: An original film slide or negative.

TYPE I: A 1st generation photograph, developed from the original slide or negative, during the period (within approximately two years of when the picture was taken).

TYPE II: A photograph, developed from the original slide or negative, during the period (more than approximately two years after the picture was taken).

TYPE III: A 2nd generation photograph, developed from a duplicate slide or negative or wire transmission, during the period (within approximately two years of when the picture was taken).

TYPE IV: A 2nd generation photograph (or 3rd or later generation), developed from a duplicate negative or wire transmission, during a later period (more than approximately two years after the picture was taken).