Anybody notice that "Nintendo" is written between the teeth on the PCB of the card?
Now, I just looked at my DSTWO, and unless they made some special version that said "Nintendo" on it, that's NOT a DSTWO. Likewise, I can't imagine any flashcart would have "Nintendo" on the PCB. Granted, I have only ever owned this (which has no markings), an iTouchDS RTS (which also has no markings) and an R4 Revolution for DS (and you guessed it, no markings). Official cartridges, however, do have certain things written on them. Pokemon Platinum says " DI Y-7 005-20" on the back between the teeth, while Advance Wars Dual Strike says " Nintendo 003-01" between the teeth.
As I have never owned an Acekard, I can't speak for it. But I find it unlikely that would have Nintendo printed on it. But then, if it WAS Alex Rider, it wouldn't (probably) be giving CRE's (unless the contacts are fucked up or there is a scratched trace somewhere).
Conclusion - I don't even know.