It was tried by Nintendo in Japan for Disk System which use floppy disks as a medium for Nintendo's Family Computer(NES in outside of Japan) As a physical DRM

It was tried by Nintendo in Japan for Disk System which use floppy disks as a medium for Nintendo's Family Computer(NES in outside of Japan) As a physical DRM for the floppy disk with Nintendo logo shaped relief on it. The floppy disk reader recognize the relief and validate the disks. Soon, third-party started selling compatible floppy disks, Nintendo sued them for trademark violation. They lost. The court concluded that mere protocol can't be trademarked even if it use trademarked logo.