When in doubt, throw it out.
That said, there are certainly still cooks out there who make fantastic historical cornbreads, though the old recipes have often been changed to include modern techniques and ingredients.
Many of America's historical cornbreads were staple breads for people who didn't have many other options.
If you have a busy natural foods store in your community, give their bulk cornmeal a try: high turnover means the product will most likely be fresh. And if the cornmeal is organic, all the better.
But since you're asking me, I'll tell you my opinion: all cornbread is authentic, as long as it's good, hot, and made with love and fresh ingredients.
I tested a lot of old cornbread recipes and most of them were bland or tough.