There was no LSD option from the factory, and whilst I believe they are available, I believe they are also quite rare and expensive. on the other hand, inexpensive lockers are plentiful.
Chock the front tires, jack both rear wheels off the ground and put the transmission in park (automatic) or first/reverse (manual), hand brake off - rotate one rear wheel and observe the other - if they rotate in opposite directions, it's an open diff; if they rotate in the same direction, it's either limited slip or a locker.
Please note - this is not a guaranteed test method - certain types of limited slip diff, the torque sensing or torsen styles, will behave like an open diff under unloaded conditions.