Hi Elmo,
In short, your Ebay listing looks legit. It looks like a decent seller [with good reviews] and a legit microphone. I wouldn’t worry. You will have a good mic to record with.
The long story is a bit more complex. Mark from Microphone Boutique explains it in this video:
https://youtu.be/W16Epa7CW64?si=FNM7lOS5pOkextjf
I’m a bit of an Oktava collector and I did quite the digging. His story checks out. Most Oktava mics out there are legit, they are real and made in Tulsa, Russia. There is only a very small percentage of counterfeit mics made and distributed. And there are some pages on the internet explaining how to spot them. But they seem quite obvious to spot. And almost all of them are MK-012 models.
What makes it a bit difficult, is that there are also a bunch [Mark says about a thousand in his video] Chinese-made MK-012’s out there, labeled MC-012. You could say they are fake, but more exact would be to say that these are very good copies. The distributor back then, ASM, wanted to increase production and overcome some quality control issues. They went behind Oktava’s back and had a Chinese company make identical copies based on original and detailed schematics and plans. Oktava found out and canceled their distribution deal. I have some of those MC-012’s, and though they are not ‘the real deal’, I can’t really hear the difference. And they are easy to spot [because of the MC-012 and A.S.M. print on them].
To make it even more confusing … some of the Tulsa-made mics were also marked with a ASM print when distributed through that company … Are you still following?
Anyway. I’ve seen a bunch of these MC-012 mics offered, but I’m not aware or haven’t seen any counterfeit MK-319 or other models. If anyone has, I’m curious to find out.