i have never heard of a .30 Luger before this thread. I have heard of .30 Mauser. . 30 Mauser is indeed diminsionally identical to 7.62x25 (AKA 7.63x25, AKA .30 Tokerev) but 7.62x25 is loaded significantly hotter. 7.62x25 SMG ammo will catastrophically destroy a luger or broomhandle.
I recall reading that Germany was prohoibited from manufacturing many firearms in mil9mm during the ijnterwar years due to the Treaty of Versailles and that is why they resumed production in .30 Mauser.
OK just read up on it some and it looks like the .30 Luger was an oddball chambering for a handful of Swiss and Finnish pistols and for the civilians that were prohibited from owning .30 mauser or 9mm. I'd want to get a chamber casting done to verify the caliber and then consider getting it reamed to .30 mauser.