RSHA/SD Insignia

[Johan Friedrich Brandenburg]

So everybody knows the standard SD uniform- A grey Gabardine jacket with SS rank insignia + empty left collar patch, empty cuff title and the sleeve diamond.
But if one looks deeper into the uniform insignia he will find SD uniforms with OrPo epaulets, NCOs without collar tresses and members of other RSHA agencies wearing the same uniform.

So here are my questions:

1.Which ranks under CO's were used by the SD?

2. When did SD use OrPo insignia and why(and can someone explain the Sturmscharfuhrer-Meister SD rank) ?

3. Is it true that Gestapo members had their own variation of the SD sleeve diamond that could be identified by the silver piping around it?

4. I saw a few photos where an SD official (not once was it a CO) with a short silver cord hanging from the belt, can someone identify what it is and what its purpose was?

5. There are some early photos of SD members below COs that had a black & white piping on around the collar patch, why and what happened to it?

Thanks for helping, have a good day comrades!