Open or LSD?

[Turbo Ready]

Hi Guys,

I started a thread requesting information about the e28 535i gearbox but it seemed to have pulled a Houdini on me. It was either tossed or got deleted during the server crash. I was hoping to post this question on the same thread.
The guys who did respond to the initial thread however, were all correct with the info given as I now have the gearbox out and it confirms what they said it was.

I just pulled the diff and thought it would have been an LSD since it came from an e28 87 535i I am a bit confused because the diff tests as an open one but yet the top has some indication of having the 2" stencil "S" on top as in the pic.

I tried brushing the stub axle bolt tabs but still can't see any proof of it being an LSD.

Any ideas?

Thanks.