7.65 1918 question

[Dave Sanders]

I had a guy call me and offer me a luger for sale, but I have what may be a dumb question as this caught me off guard a bit and need a bit of clarification. He said it is a 1918 dated luger but in 7.65 (30 luger) cal. There isn't another date stamp on it but he said the gun is matching except some other numbers were added to the toggle part, but the barrel matches to the gun, too. I know it sounds confusing as it did to me, but is sounded a bit like an after war job to me. Now, here is my question: there weren't any 30 luger made guns that would be dated 1918 would there? Weren't all WWI military guns 9mm? Didn't the 30 luger caliber come in after the war or were in commercial sales? The guy said he has a fairly new book that says 1918's could be both. I have not heard that, but didn't want to argue with him. I am going to try to look at it tomorrow, but wanted some clarification to myself before I go.Thanks for any help you may give.
Dave