Easiest way to tell is the seats.
If they're all black leather Recaro, ST3. If Partial leather Recaro, ST2.
ST1 (I know you didn't ask) - All cloth, minimal bolstering.
ST2 - Partial cloth/leather with special texturing and bolstering. Inserts can be Yellow, Red, Blue, Gray.
ST3 - All black, smooth leather, largest bolstering