I can perhaps give you some help---coupled with a SWAG---or two or three. We'll see how it goes.

I had a Satin blue K-22 I returned to be refinished in Bright Blue. It came back with the markings S <> on the several pieces---(S&W finishes/refinishes guns in pieces). In this instance, I decided S <> translated to S= Return to Service Department---<> = Bright Blue. So much for that.

My best guess (assuming the S <> appears no where else on your gun) is, 1. The barrel is a replacement, and was finished/refinished in bright blue. If those models are finished in both Satin and Bright Blue, it's pretty much a lead pipe cinch it (the barrel) started out either in the white or in Satin Blue. I'm told (by Jinks) the Service folks work on one gun at a time, with no parts from other guns on their bench (negating the need to number replacement parts)---hence no number on your barrel.

A letter will tell you the specs on your gun when it was first shipped. If we're lucky, it shipped with other than a 4" barrel, so there will be no more wondering about that. Otherwise, don't sweat the small stuff---the gun is what it is.

Ralph Tremaine