I am surprized nobody previous to me pick up on the fact that your 629 has the interchangeable front sight. The clue that confirms that you have the interchangeable front sight is the position of that pin, it's biased towards the front of the barrel and that pin is what the front of the dovetail base is what holds the sight in place with a spring applying the pressure.
DO NOT drive that pin out, if you do you'll regret it. Instead, all you have to do is push the sight straight toward the rear of the gun against the spring and once it's all the way back, tip the front up and out of the slot. Once you've figured out how easy it is to change the sight on the models that feature this type of mount, you'll then want to look at S&W's site under the parts/sights category, they have a good selection of different sights you can change out at will.
BTW, if you haven't picked up on it yet, I am a HUGE fan of this system. Frankly, I wish that S&W offered this type of mount on all their revolvers because it makes it so simple to change the front sight and slip in a blade better suited to a specific task.