Gott Mit Uns would be a motto found on German Army buckles in the WW2 era, but the Death's Head is an SS insignia; the SS motto on their buckles was Meine Ehre Heisst Treue, and they had an eagle/swastika emblem, not death's head. It is difficult to see for sure but if there is an "RZM" mark on the back of the buckle, which would be intended to signify it was approved by the Reich's agency inspecting official clothing and insignia, it is very probably a fake, of a type that didn't exist to the best of my knowledge.
(Edit: I was composing this at the time Sieger was writing his post.) I have little knowledge of WW1 insignia. I seem to recall some units used a Death's Head in WW1 (Hussar?) but I thought they might have used the earlier jawless skull, not the later Waffen SS style deaths head shown here. That would be worth checking into. If one were interested in buying this, I'd get a description of the makers marks on the back, in particular asking about an RZM mark, which has a circle around the letters built into it. If it has one -- BEWARE. Otherwise, I would run, not walk, from this one barring having specific knowledge about it. Hope helpful!
John
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John
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