I'm sure you just got a new one. Mine is an MK1, Second Edition, and runs stably in most apps at 312 MHz, with a max of 320 MHz. They all use MMSP2s, the same model even-- no matter what revision. But as time goes by faster cores will eventually find their way into MMSP2s, odds are. e.g. 400 Mhz ARM9 parts marked down to 200 MHz might end up in there someday. Seems 266 MHz parts marked to 200 have been being put in for ages now.