What is this part called...

[siegersallee]

Thanks mrerick, for the link...I will study it and learn from it.

Thanks John, I will follow your steps to learn more...

Now I have one more question...

I have seen ads that advertise their Erfurts as all matching; but, I have noted that the proof stamp supposed to be on this pin is missing.

Does that mean the pin, ( "backside of the magazine catch" ...see pic above ) is a replacement?

Does the claim "all matching" include the stamp that is supposed to be on this pin?

thanks,
Richard