CraigC
Sixgun Nut
The upgrade started with the Magna Classic but they all got it after that.The Classic models had what they called the "endurance package" which was where they may have done some other stuff (I dunno) but they also added radius in areas where sharp corners previously had been (reduce stress).
Don't know when the reg 629's got the upgrade. Pretty sure the last of the all silver 629's (-3 I believe) do not have it.