You're probably fine, I only heard a rumour that there are fake mkh416s, but never encountered one on ebay/reverb. That doesn't mean they don't exist.
It's getting difficult, I've been buying audio equipment 2nd hand for decades now 😬 and this is happening for like 4 years now?
This is two years old video that helped a friend not to buy a fake U87Ai for more or less typical 2nd hand price of the original. It was slightly cheaper then normal, but only very slightly. And that's only because he could see it in person and also look inside.