Sort of. It used to drop off a Wastewander Bandit, but they were wiped out in the Cataclysm. Six months or so ago, Blizzard brought the Tough Scorpid recipes (including the Breastplate) back, but as Bind on Pickup recipes that are zone drops in Tanaris. If you just found it on an old toon, I'm guessing it's the old kind of recipe, so it's Bind on Equip and can be sold in the auction house. That would make it valuable to someone too lazy to farm the recipe, so it should have some decent value, though not what it would have if it had stayed out of the game (like most of the Heavy Scorpid recipes did).