First off, Welcome to the forum. And as for your location, keep your head down.
My copy of the SC of S&W III mentions only 2" square butt guns. But with everything S&W, never say never. It may have been converted along the way too. A good picture of the grip area with the stocks removed would help.
Thanks for the info. I dont think its a factory RB and was converted by the previous owner. I've been thinking of having it refinished when I get home from this tour and getting a nice set of custom grips made for it. Its been a great companion for the last 24 years.