These Greek plates do occasionally come up for sale on Ebay. None of them are official Greek plates. In Greece, the only legal plates are those supplied by the government and all have the official seal stamped into them. The sign shops in Greece will make all sorts of plates that look vaguely like real plates and some people do this if they lose a plate and are waiting for the official replacement.
However, if you want to collect plates from Greece, these are basically fakes