Elongation of Hammer Nose Opening

The hammer nose snapped in my old school prelock M66. I fixed it, thanks to help from forum members :)

But now I am wondering why it snapped to begin with. If only for curiousity purposes. Well, in my reading and looking for spare parts, it seems like theres two versions of hammers for the old smiths. Some have springs behind the hammer nose and some do not. I am not sure about this change technically, but what I am guessing is, the spring keeps the hammer nose pointed downward which prevents the hammer nose from smashing into the frame of the revolver. In the original broken hammer nose, there was no spring. The hammer nose just flops in the hammer.

Inspecting the revolver, I see an elongation in the frame, it's assymetrical so it appears to be damage and not intentional from the factory. I am guessing this is where the hammer nose smashed into the frame, multiple times probably, causing wear to the frame to elongate that spot, and ultimate snapping the hammer nose in half. Actually as I look at what might have impacted into that groove, its probably the top of the old hammer nose that was hitting it.

Unless that elongation is supposed to be there? It appears to be slightly skew to the left and my second S&W pre-lock revolver doesnt have that same milling and also never snapped its hammer nose as I've owned it. Although my second k-frame also appears to lack a spring behind the hammer nose so maybe my theory is off.

https://i.imgur.com/kSRNomU.png

https://i.imgur.com/PHpomKJ.png

That is milled into the frame during production for relief/clearance of the hammer nose.