Thanks for the replies fellas,
I did some more searching and found this recent
thread .
In it, Demon states that you should immediately be able to tell by pulling the intermediate shaft. This ought to be easy since the tranny in question is not on the car

.
What I'd like to know is, what am I looking for to differentiate an open diff v. an LSD? A metal casing, (in)ability to see through to the other side? etc.
TIA, again.