Regarding full-size (aka half-height) LG DVDRW drives:
No drive with a model name starting with GSA-H... is faster than 20x. Most top out at 18x.
The fastest LG PATA DVDRW drive I know of is...well, probably the one Alan listed above, something with the newer model naming scheme of GH22NPxx or GH22LPxx.
To get a 24x drive, it would have to be SATA, so you'd end up with a model name of GH24NSxx or GH24LSxx.
...If the drive is pulled from a computer as an OEM drive, then the drive name would be shortened to GHxyz -- something like GH30N -- so 5 characters total. There's no direct way to compare the short OEM model names to the normal LG model names & determine speeds, but you'll still not see a 24x PATA drive.