Im not sure when the LSD became standard on the e36, but 1996 would probably have been it, since it was when most of the changes were made. The easiest way to tell is go do a burnout. If you leave two tires marks, then you have LSD. If you only leave one, then you have an open diff like the previous models.
<span style='color:gray'><span style='font-family:Courier'>1995 e36 3 Series RIP
1999 e46 3 Series BURN IN HELL
2000 MR-S Roadster= Current</span></span>