There are four major varieties of .32 Bisley Single Six.
RB32 is the base model (RB = Ruger Bisley, 32 is caliber) and then add "A" for Adjustable sights and/or "W" for roll-engraved cylinder (or Woll-engraved, I guess... don't ask me why Ruger chose "W" for that).
So the four flavors are:
RB32 = Fixed sights, fluted cyl.
RB32A = Adj. sights, fluted cyl.
RB32W = Fixed sights, rollmarked cyl.
RB32AW = Adj sights, rollmarked cyl.
Here they are, from left to right - RB32AW, RB32, RB32W, RB32A:
Of the four primary types, the RB32A and RB32W are the rarest.
There were also two types of RCA guns with stag grips, and some minor variations like "arrow" stamped guns (a forum member has one of those).
The same catalog scheme applies to the .22 caliber Bisley Single Sixes - there were models RB22, RB22A, RB22W, and RB22AW.
In the blue Bisley Blackhawks, all guns were adjustable sight, but the "W" was used the same way. There were RB35 & RB35W in .357 Mag, RB41 & RB41W in .41 Mag, RB44 & RB44W in .44 Mag, and RB45 & RB45W in .45 Colt. The rarity of the Bisley Blackhawks goes something like:
RB45 (rarest)
RB41
RB41W
RB35
RB44
and then the other "W" guns were made in fairly high quantities.