From d&d's website (courtesy poster sanjhd):
"Directly from what Doug Mckenzie told me, there are no such thing as Brown SplitSpades... HOWEVER, there were plans to make both Gold and Brown SplitSpades. These plans were carried out, by first printing the Gold and Brown boxes (around 1000 or so of each, I'd assume), and then, printing a few uncut sheets of gold and brown splitspades. Though, when the cards came out, they looked awful (the gold/brown splitspades), so now David Blaine's crew was left with 1000 gold/brown SplitSpades BOXES.
So, instead of trashing the boxes, they simply put in blue/red decks into these Brown/Gold boxes. The boxes look pretty cool, and the cards put into these decks come in the MNEMONICA stack.
So, basically, Brown/Gold boxes EXIST, but the brown/gold cards do not. They are simply just red/blue decks in the brown/gold boxes.
If you really want to get one of these gold/brown boxes, you might want to contact Doug or David.
Hopefully this clears everything up.
All the best,
-Sanj"
Also, they're in stock at davidblaine's site.