This must have been done differently in different eras. On some of my guns the front sight BASE ( ramped) is held on with two pins and others ( 14-3, 14-3 and a early K-38) with a single pin. All these later mentioned guns have the blade itself looking solid with the ramped base. I've got some N frames that the blade itself is pinned with a single pin.

My 17-3 was showing some rust coming out of the junction of front sight base to barrel. I removed the pin and never did get the sight separated from barrel. I wrote about this somewhere on this forum asking if it could have been silver soldered in place as well as pinned and got the opinion "no." I gave up getting it off and just make it a point to saturated the area of rust as often as I look at the gun. On that gun, the pin itself was VERY difficult to remove and I had to DRILL it .