I don't know the new German proof laws that well (though they probably have not changed much) but in general proof houses do not prove parts. How would a slide fire a proof load? That is why percussion guns sold as parts kits are not proved.
If Rick35ovi can find a CAGE code on the slide (a five character alphameric like 3M256 or 72AX2 (I made those up), we could trace the maker.
Jim
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