Yes, they were SUPPOSED to be marked, but not all were.
I have perhaps 18 - 20 rifles & pistols that I'm positive are imports, mostly RCs, that are neither importer or RC X marked. A good example is a P.38 in the box from the importer with a ruskie inventory sheet listing 20 P.38s including mine - neither an X or importers mark.
While perhaps NOT common, it is also not a rarity.
I also had a PPK that was importer marked indicating it was brought in long after the import ban on PPKs. Nothing should be a surprise when it comes to imports.
Sarge