2. The studs aren't Miki - or, at least, the findings aren't Miki.
3. This stud is rather poorly set. You should not be able to see beneath the cup. If this was purchased as preloved Miki - I'm 100% confident it's not. If it was purchased from another vendor - that vendor should fix it for you free of charge (QC issue that it shouldn't have gone out with).
Again, apologies if any of my commentary has already been covered in text.
Mikimoto grade differences will be hard to determine by photos. Take comfort in knowing that the Mikimoto brand features top quality in all ranges (A - AAA). It would be worth it to have a full insurance appraisal done by a qualified appraiser or authorized Mikimoto retailer in your area. Hope this is helpful.
I can see text like usual here now.
Sl sorry @SGV_Gal!! @Pattye is totally correct. My eyes were playing tricks on me, that stud is just fine! What I thought was the pin is just a reflection off the surface of the side of the cup lip. So many apologies for scaring you!!
I didn’t realize the studs weren’t part of the newest acquisition, but FWIW - if the findings do come loose one day - it’s an easy fix. I’ve had to fix a couple of pearl studs for exactly the reason @molinePDG’s brought up - summer heat and east coast humidity in just the right amounts does a number on some types of glue!