re: What is this?

Visually it looks to be black locust, however, not having a leaf or two, your next best bet is visual inspection of the end grain under magnification. Barring that, below I’ve provided a useful link for future reference. About a third of the way down the page, you’ll find an additional link to the Center for Wood Anatomy, the USDA’s Forestry Products Laboratory, where you can have up to five specimens identified per year, for free. Happy hunting!
http://www.wood-database.com/wood-articles/wood-identification-guide/