SS-marking on luger

[Dieter08]

Hi guys, here is a not so good pic of what we are talking. It's my Erfurt from 1913. The stamp seems for me to be real because the right wing of the eagle and the "1" of "Wa" is not to see because the gun has some deep rust-marks, also on the stamp! If it is a fake, how did he deep-rust the eagle???