I have not learned about a V on his Bronze. The claim I heard was about the Silver.
Kerry's Bronze Star was awarded with a 'V' device, as it was awarded for combat. (Bronze Stars can be given for non-combat related activities)
However, there has NEVER been a 'V' device awarded for a Silver Star, as that award can only be given for valor in battle, making a "V' award redundant. No service has ever given out a Silver Star with one... until Kerry, it seems. His records indicate a 'V' device, making the record bogus.