What do you men by "current-model SW 686"?
Is it a no-dash 686, or do you mean it is a 686-7?
It it just the two cylinder bores that exhibit this, or is it all of them? Looks like it may be from worn bits in the cylinder boring machine. In the manufacturing process, all six holes are bored simultaneously using six separate bits.
Of course, it could also be the result of Bubba, the kitchen-table gunsmith, trying to open up individual cylinder throats.
Besides that, the photo makes it look like a 586 - probably just the lighting.