Those that said bow quiver were correct. Those are arrow brackets for an old quiver style that was popular in the 50s and 60's, but the quiver was still sold as a cheapee alternative for many many years after that. There is a plastic hood shroud that goes with that is missing. The hood shroud actually clamped onto one of the arrows in the quiver to form the hood. It would have been clever if it actually worked, but they were very unstable and also did a lousy job of covering the arrow points as well.
I can't recall the exact name at the moment but I may still have parts of one around here somewhere.