According to a latest report published by MICgadget, engineering prototypes of iPhone 4 64GB are selling in grey markets of Hong Kong. They say its not 100% confirmed whether there iPhone 4s are the real deal or not but its pretty intriguing to find out that Apple might be working on these prototype 64GB models. These limited quantity models have been found selling in Sin Tak, the biggest grey market of Hong Kong. It is quite strange to note that the back of these iPhone 4s states iPhone XXGB!
Furthermore, the backplate of these 64GB models states Model no. as XXXXX, and the FCC ID as BCG-XXXXXX. On the image below, you can see it is indeed a 64GB capacity and the model is 995-6049LL. Interestingly, this iPhone 4 is also factory unlocked!