I am pretty confident it is a gun sight. But, to what, I have not a clue. Thanks for your ideas.
Again, what makes you think it's a gun sight, and one from from WWI? As I've asked, are there any markings on it?
Being "confident" isn't the same as being right. If you really believe it is, tell us why or what evidence you have to support that theory. I have yet to find anything remotely close to it, so I am curious as to how you came to that conclusion...
Is that centered bolt hollow?