Woops!...I didn't realize that the model # was stamped on the pistol, although, considered in hindsight, I should have thought to look for it. How embarrassing. In my (weak) defense, it's my wife's pistol, and I didn't have it in hand when I responded to Crazy K38's post.

At any rate, I checked the frame underneath the yoke hinge, and it is a model 649-4.

My thanks to Crazy K38, JKC, and 2Hawk for your patience in explaining the location of the model #.