Dave B;
Yes on the guns with frame mounted sears this is the pivot, as you state. The Sear end itself serves as the firing pin retainer. On plate mounted sears this screw serves only as the firing pin retainer. All of these I can recall noting were screws. The Sear pivots can be either. The screw/pin is not in the exact same location on both but is in same general area.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra