Bests & Worsts Reviews from Amazon

I fell upon this titanium flask as I was searching for one that wouldn't rust and wouldn't give off a metallic taste to the liquids inside. When I received the flask, the first thing I noticed was that it was made fairly well. It was lightweight and seemed sturdy. The problem came when I shined a flashlight into the flask. The bottom of the flask(inside) had some weird brown/black discoloration on it and the seams were brown(rust?). I was under the impression that this was 100% titanium, which shouldn't rust, but I guess there is some other type of metal being used. I have contacted Vargo customer service and am waiting on a response. I have attached a picture to show what I see inside the flask. It isn't a great picture but you can see the discoloration I am talking about. I have even tried to add boiling water into the flask to clean it out, but the discoloration is still there.