Nintendo Logo Disk Protection
Antipiracy Rare System
Modifications to the standard Quick Disk format include the NINTENDO moulding along the bottom of each Disk Card.
In addition to branding the disk, this acts as a rudimentary form of copy protection - a device inside the drive bay contains raised protrusions which fit into their recessed counterparts, ostensibly ensuring that only official disks are used.
If a disk without these recessed areas is inserted, the protrusions cannot raise, and the system will not allow the game to be loaded.
This was combined with technical measures in the way data was stored on the disk to prevent users from physically swapping copied disk media into an official shell.
However, both of these measures were defeated by pirate game distributors; in particular, special disks with cutouts alongside simple devices to modify standard Quick Disks were produced to defeat the physical hardware check, enabling rampant piracy.
An advertisement containing a guide for a simple modification to a Quick Disk to allow its use with a Famicom Disk System was printed in at least one magazine.