There is no law against selling such a magazine in Tennessee. Further, the federal ban against selling large-capacity magazines expired in 2004. Even when the ban was in effect, however, magazines made prior to the ban going into effect in 1994 could still be sold. I ran afoul of ebay's policy forbidding sale of any magazines, but my selling it was completely legal.
I'm pretty sure that the sale of large-capacity magazines is only illegal in half a dozen states; California, Hawaii (handgun only), Maryland, Massachusetts, New Jersey, and New York.