James, unlike the US that only recognized the receiver as "the gun", German gun law considers frame, slide and barrel equally "essential gun parts" (each of which can get you napped for illegal possession for example). As such, they all get the eagle stamp as part of the process. The actual overpressure proof mark is the mark of the proof house and date.
I used to love being able to hit hard at 1000 yards. As I get older I find hitting a mini ram at 200 yards with the 22 oddly more satisfying.