Receiver rail guide.

[sheepherder]

1969goatman - Can you post a closeup pic of the inside part of the abutment (like the pic above) so we could see how badly the abutment has been battered??? It's been said here that the "Mauser Hump" was incorporated into the grip frame to eliminate the problems caused by excessive 'abutment' battering (namely, the toggle axle pin becoming fully exposed in recoil and popping out)...

In fact, if it seems to you that it is 'battered', maybe post a pic of the assembled pistol w/toggle in full recoil (you'll have to hold it back with your hand) showing whether the toggle axle flange is fully exposed...

Here's a pic of my S/42 (same gun as pics above) showing the relation of my toggle axle pin to the frame ears, in full recoil (I'm pushing it back with my finger), and having the breech block imprint on the 'abutment' as shown in my pic...Not too bad, even considering this frame does not have the "Hump"...