The 3rd Edition of the S&W Standard Catalog (Page 257) shows:
629-7 New Two piece barrel in 2005
629-8 Slabside Barrel 2006
However, my 629 does not have the slabside barrel, so I believe the change must be attributed to the frame, irrespective of what barrel is installed.
Picked up a new 629 5 inch barrel pistol today.
My last info regarding changes to the 629 ends at 629-6. Does anyone have any info regarding what the -7 and -8 changed or improved?