Here is the flap on my S&W 686-3, can someone break down these abbreviations toward the right that are SB and RR for me.




I was guessing RR to Red Ramp for front sight?
The 'S' being stainless. Stock however 'SB'?

Is there any meaning to the 284 above model No.?
Any meaning to the 'M' above features?

There is also a 1988 dated warranty service center foldout, kind of neat to see some of the names on it, Bill Davis Service CA, Clark's Custom Guns LA, Terry K Kopp MO, John Jovino Co NY

Thanks
Karl