The tag is a scruitineer checking item. It shows if the restrictor (or turbo) has been tampered with after its been checked with their verniers for size compliance.

It will have some numbers / markings on it which can be traced back through the powers that be if the car has a motorsport log book.

A taper threaded plug is sometimes used to bung up the holes left by these sort of grub screw restrictors after removal.

Are you gonna use it (the car) or break it ?