26331st Ap / grey mkt question

[305watchcollector]

Hello,
Hope everyone is doing very well and especially healthy during holidays season.

Roughly, 4.5 years ago i helped my younger brother source a ROC reference 26331ST panda. He purchased it on the grey market via trade, trading in several old hublot/IWC watches. The dealer is very reputable, local, and well referenced. Luckily the price early 2019 was still not crazy for ROC and the trade was at MSRP price which was market standard at the time (considering these were at the time readily available at the boutique).

The watch came with everything, box, papers, tag, even stickers. Furthermore, the warranty number and watch was immediately registered under my brothers name in the AP website and warranty was extended to cover 5 years. Nevertheless, being a paranoid individual, i decided to have the case back opened just in case with a local watchmaker in florida that has been working independently for over 35 years. Attached please find pics of when i had the watch opened a couple of years back.

I wanted to share because i have been reading horror stories where clones are made with real serial and warranty numbers allowing collectors to register watches online in AP website. This is especially scary for watches, such as this one, that come with a closed case-back. I also wanted to share pics of the movement to ask collectors how it compares to the newer open display references. Finally, I know the watch was opened by a professional and i was told like 5 times everything is perfect, but if experts can just triple check, would be much appreciated.

Given the horror stories shared in the forum, aside from buying the seller and opening the watch, what else can collectors do to buy with ease outside the boutiques?

Forgive my english as it is my second language. Wishing everyone a great and healthy holiday season.