DW vent ribs
Yes, the V indicates vent rib. The one shown doesn't have a vent rib so I guess it is a plain old 715, not a 715V. My 15V6 has a vent rib as does my 44V6.
Again, 15 refers to the mid size frame .357s, a 7 in front means stainless, V means vent rib and an H means full underlug. If this is followed by a number such as 4,6, etc., it refers to the barrel length. The large frame 44s use 44 instead of 15 in the model designation.
Bill