I'm quite possibly the lowest on the S&W brainpower scale here but I'll bite to help you out. The "dash" is just the engineering change number. The first run of a model will be the "no dash", then they change somthing and add a "dash 1", as in 29-1, or 629-1 . When they eliminated the pinned and recessed features on the Model 29, that ended the 29-2 and started the 29-3 era.
As for the 629, I believe the 629 "no dash" was the only model with pinned barrel/recessed chamber features . They were eliminated when the 629-1 came out a few years later.
IMHO for your first Smith I wouldn't get too caught up in the p&r, "no dash", and all the other hype (like we all do

)
If you find a tight gun with a good action you'll be set for a long time, no matter what dash it is. You'll have plenty of time to start collecting the real goodies when your hooked.
