The System II and III tremolo systems use a height adjustable locking nut.
The System II tremolo system was designed by John Page, Chip Todd and Charlie Gressett.
Serial numbers show approximate date of manufacture.
For all dates, you will need to look at the construction technique and components used to get a more precise date of manufacture.
The Fender Contemporary Telecaster models used the same tremolo systems as the Fender Contemporary Stratocaster models.