I found a passage in the Nordschleife rules which says that cars with temporary number plates are not allowed on the ring.
Just wondering: Aren't people from the US with ED driving around with number plates like these?
That are number plates for exports (so called "red numbers") and it looks to me, that cars with these aren't allowed? I don't know for sure and don't want to make anybody nervous, but I would clearify that point in advance.