Who knows when it is from. But it feels like it's kind of new, maybe 2005s and beyond. But noone knows.
Brother. Why sit on something the fans love? What is the harm of releasing it? It's just an ego thing. "this is too good to be released I'm just gonna play it live and not release it."
That's asshole tactics. Makes no sense. What if he died, God forbid, and it was forever lost in his hard drive?
No, the right thing to do is to release it.