A prototype iPhone 4 with T-Mobile 3G has been spotted and photographed, suggesting Apple is considering adding the carrier as a third option in the U.S. Boy Genius Report states that the prototype carries an internal model number of N94, different from the N92, which is the Verizon iPhone, and N90, which is the standard GSM variant of the iPhone 4. Although T-Mobile USA uses the GSM standard, its 3G bands are of a different frequency than most other GSM carriers, explaining the need for a specialized handset. Meanwhile, citing code found in iOS 4.3, 9 to 5 Mac claims that the “N94” designation of this prototype means that it contains an S5L8940 processor, which is another name for the A5 chip. A report from last week indicated that Apple was seeding select developers with A5-powered iPhone prototypes that look “virtually identical” to the current iPhone 4 save for the processor inside, however, this alone does not explain the T-Mobile 3G-capable hardware found in this latest prototype.