Are they back door genuine "after market" or some kind of copy? I don't know.
Makes you wonder if half the W5x boxes we see are real?
There was a company many years ago back dooring Toyota genuine parts in from Japan and flogging the dealers with them, can't think of the company name, they where bought out by repco, but they specialized in gearbox's.
I have seen from time to time crated W58 up for sale on varies forums and sales sites.
But in saying that, you would think, the way the Rolins like to price things if they were the real deal, they would wear an extravagant price tag.
Might be worth a call.