[HerrKaiser]

You are correct in your assessment that this was a WW1 gun that was reworked and re issued in the Weimar forces. The holster is in fact a commercial holster but looks like a US commercially produced holster. It is also a Nazi magazine, they switched to aluminum based mags in the early 30’s but it has the Nazi stamp from the look of it. It’s also a spare mag for whatever gun it originally belonged to as evidenced by the plus on it. The bad news, from the pictures I see, it’s looks as if it has some shallow pitting all over the gun. This reduces it to shooter status despite its all matching numbers on the gun. That said, welcome to the forum! Enjoy your new purchase, these guys have lots of info on here to soak up, I still am!