What is the meaning of Die_plate?

A die in the form of a metal plate.

1. A type of die for cutting screw threads on male fasteners; it is arranged in the form of a plate of tool steel with a graduated series of holes, each being the die opening for a certain size of screw. A predecessor of today's tap and die sets, it is now considered an antique type of tool, no longer in common use but still sometimes desirable as a collectible among tool collectors.

A type of die for cutting screw threads on male fasteners; it is arranged in the form of a plate of tool steel with a graduated series of holes, each being the die opening for a certain size of screw. A predecessor of today's tap and die sets, it is now considered an antique type of tool, no longer in common use but still sometimes desirable as a collectible among tool collectors.

A metal plate that is part of a die.

Source: wiktionary.org