First off, this guy sounds like he really likes you. If he is giving you something that means that much to him, then he obviously thought about it a lot, which would mean that he most likely has no regrets. If there is no way that he is taking it back, then you should definitely keep it, I mean there isn’t really anything else you can do. Keep it very safe, where nothing can happen to it, just incase he really does want it back later.
Sometimes allowing someone to do something for you is the kindest act you can do. Therefore, I think you should accept the gift from him. If things don’t work out between the two of you, offer to give the gift back to him, but for now, enjoy the relationship and the fact that he’s opening up to you and showing you a part of his life that is precious to him.