According to the report, these new iPhone 6 PCB images revealed that the serial number format is consistent with those of previous iPhone models but has a different numbers compared to the iPhone 5s. This suggests that these boards are indeed internal components of the next generation iPhone.
“Although the components that will eventually settle on the circuit still missing, the photos below reveal their respective serial number ie 820-3675-04 for one and 820-2486 – 09 for the second, format commonly used by Apple to make motherboards its smartphones,” Steve Hemmerstoffer writes for NowhereElse. “The motherboard embedded in the iPhone 5s (center photo below) is, for example identified in the reference 820-3382-06.”
Finally, the report warns that they are about 90% certain that that these leaks are the real deal.