I can't say for sure, but you've given a few clues.
Locust is often used for fenceposts. It doesn't rot, or at least takes forever to rot. Also, locust grows fast, and I see wide-spaced growth rings in the cut ends. And, contrary to what one would expect of a fast-growing wood, locust is very hard. So, for those three reasons I'll place my guess on locust. Black locust, or honey locust, I'm not sure.
When [url="http://www.EverydayHunter.com"]"The Everyday Hunter"[/url] isn't hunting, he's thinking about hunting, talking about hunting, dreaming about hunting, writing about hunting, or wishing he were hunting.