I purchased a set 3-W , no serial numbers on hosel, nothing on ferrules, looked very nice, that being said, after speaking with Mizuno in USA and Australia, they couldn’t confirm from that information.
The tell tell sign to confirm counterfeit was parallel shafts, Mizuno could confirm their irons are all tapered .355 shafts.
Seller was very accommodating, sent postage paid label and fully returned purchase price.
Hopefully next set will pan out ; gotta be a top notch detective these days.