That's weird - I just saw one of these on Ebay the other day. And my local Gamestop had 2 of them available for purchase on release day of AC3. I'm not sure if they were the exact same ones, but they looked pretty similar. I was going to pick one up, but after spending the $100+ on the limited edition, I figured another $40 or so was just too much. I haven't seen any for sale anywhere else since then though, so can't vouch for the rarity.
Edit: Oh, just saw the "limited edition" numbers, I don't know if the ones they were selling at Gamestop had those or not... I'm thinking probably not... carry on and nice find!