What is the story on this odd Old Hickory shelf?

by Wes
(IL)

I recently acquired this double shelf. It has metal rings at the top rear and bottom front. I presume the top rear ones are for hanging it on the wall? It has a groove cut in the rear of each shelf surface, and the top shelf has a horizontal bar above it. What would this shelf have been used for? The groove looks like it might have held plates? But what would the bar be fore? Also, I'd like to get an idea of its age. It's stamped 5140 Old Hickory, Martinsville, IN on the back, and has a small sticker medallion that says "American Provencial."

Thanks!
Wes