Help identifying mysterious differential

[HersheySquirts]

Hey guys,

So when I bought my car I got a ton of goodies with it for free. One of those goodies was a diff that is supposedly a 4.10. I have no idea if it actually is a 4.10 because the tag it came with from the factory is long gone and no one has marked the diff in anyway. So I did some research and still have come up with no way to tell what this thing is. I enjoy working on cars but I am in no way an actual mechanic or BMW expert. There are some numbers I found on the diff but led me nowhere. The #s are 1 210 421 and A 0G(or 6, can't tell)7 . Somewhere I read the A means an open case, is that true? It is a small case so it probably came of an auto m42 car, so it's probably an open diff. Anyway I'm hoping someone can confirm what it is so I can sell it off. The gears look really good besides the gunk that's gotten up in there.

Thanks for the help

-squirts

Pics:

[AndrewBird]

Well, I can tell you it's open just looking at it, no limited slip unit. Ratio you can figure out by counting the teeth or turning the input shaft and count the number of turns on the output shafts. Counting the teeth will be more accurate though.

[TobyB]

...and if it's open, there's only a tiny chance it's a 4.10. If it IS, and you don't want it, I'm interested- I need a 4.10 to lock to see if it's better than a 4.10 lsd on a Pro3 car.

t