Most likely a promotion for the upcoming crossover "FE x SMT" exclusive to Wii U. According to the official website, this can be redeemed on Nintendo 3DS OR Wii U. Both digital and physical versions of games will work.
Please immediately stop with the requests for codes, selling of codes and the like. There's a thread for that elsewhere on CAG, right over here:
Further posts in here with those buy/sell requests will likely risk banning in some fashion.