The 629-2 was the first "Mountain Revolver".
Has the old style square front target sight leaf,
Afaik it's the only one that came with the satin bead blast finish.
Cons are the bead blast finish will polish from holster wear and can't be easily fixed like the satin SS finish,
The dash 2 is pre endurance package so not as strong as a dash 3 and up,
The old rear sight means it's not drilled and tapped for mounting scopes or red dots etc.
When you see the box look for any marking on the box end that might say " Magnaport".
Iirc a small amount were sent from SW to Magnaport to be modified with the ports exactly Iike yours.
The Magnaporting has kinda fallen out of favor so some put them below one without it,
If you like ported revolvers it's a big plus because you don't have to send it off and she'll out the $$$.
I would look at it in two ways,
If the box indicates it was originally magnaported you could bead blast it to original finish and get a set or original style Pachmayers and put it away as a collector piece or if it speaks to you as is make an offer you can be happy with and shoot it.
Imo the Magnaports don't make much of an improvement but they do vent gasses towards the barrel front sight and sight ramp which will need to be cleaned more often.