See this quote... Rand saw this sword from his own memories from the last time he was in Falme. We know that the sword is not Turak's sword (it doesn't have a heron), therefore it has to be a sword he saw from one of the heroes of the horn.

"Rand reach down touching the sword he wore at his waist. It was the curved one, with the scabbard of black, painted with the twisting dragon, red and gold. For more reasons than one, it made him think of the last time he had been in Falme. "

I think Sanderson will not verify the sword because it may have more history than just being Justice. We know Rand's new sword is power-wrought from Min's PoV. This means it was made in the Age of Legends. Since it has a dragon scabbard it was most likely used either by Lews Therin or one of his closely trusted associates.

There is alot of history to this sword--- I don't think Sanderson wants to ruin the surprise just yet.