How many different iterations did they have for our FD's?
Were there 4?
If I'm not wrong, there was an early version painted black made by RSR with "RB" on the top of the mufflers. And then I saw a similar one except the logo was "racing beat" also on top of the mufflers.

And then there are the full stainless ones with an all polished muffler can
And one stainless system with a ribbed can.

A few different looking tips out there as well. Ones where the tips are one piece and another where the tips are two piece.

I guess my ultimate question is, which one is the loudest RB Dual?

 

Why dont you call racing beat and ask them?

 

^^ what he said is the best thing to do. Get accurate info and avoid all guesswork.