DVDInfo X is a small, ugly but useful, utility that scans your Macintosh for DVD drives and displays their RPC (Region Playback Control) status. It supports multiple drives.
A RPC-1 (region free) DVD drive will play movies from any region.
A RPC-2 (region locked by the RPC Phase II scheme) DVD drive’s region may be changed 5 times, then it will be locked.
Once locked, it can be reset by the manufacturer (or vendor), so you’ll have 5 changes left, again. Only 4 vendor resets are allowed, then the drive will be definitely locked. It can only play movies authorized for the region it belongs to.
DVDInfo X will only list DVD drives that have some WRITE capabilities, like combos or SuperDrives. You also must eject any medium that is in the drive, or it will not be listed.This is due to limitations of OS X that I could not work around.