The slippery limited slip returns

I retrieved the LSD from the junkers today and cleaned it up to find that there are NO markings on this differential. No "S" stamped anywhere to show that it is indeed a limited slip differential. Great.
So, how does one confirm that this is really an LSD? Well YouTube is okay, but I found conficting information on the site. This may have been a conversion, so the task before me is to confirm 2 things: what's the ratio of this thing and is it or is it not an LSD?

1) ratio? YouTube did have an excellent solution for this one showing a car on a lift and the tire taped and the input flange taped to show the rotation. Turn the tire 10 times and count the number of times the input shaft turns. Move the decimal point over one space and BAM! Mine turned a total of 39+ times (which corresponds to the 3.91 ratio).
2) LSD or NOT? That's a bit harder. I guess I could pop the cover off and see the guts to confirm it, but one way (this I looked up) was to turn the input shaft and see if both hubs turn. That's the first sign, but it's better to simulate what happens when one wheel is stuck in the mud or snow and see if the other hub moves and if you can keep ahold of the one you're trying to keep still (stuck wheel). I tried it and I couldn't hold the hub still. Good sign.

I kept looking back at my driving tests and this one acted like an LSD, so why not any markings to back me up? There are conversion kits available to make your open diff into an LSD. I just don't know, I guess I'll keep cleaning it and messing with it until I'm convinced.