According to a post to r.a.p by Angus McKay a couple of years ago, the Oktavas marked MK are the ones that are imported and distributed by him in the UK & US, i.e., the "legal" ones.
Unfortunately, there's no predictability on MK/MC-012s. GC gets them in lots with both naming conventions. I never saw one marked MK until fairly recently. I got a pair a while back that came out of the same carton - one was MK and the other was MC.