Thx for the comment and confirmation on the gen.
It must be me then
The PAM came with a sticker "sapphire", but, you know, I don't always believe what our Chinese friends write...
Also, sapphire usually sounds lighter when ticked with a nail. Here also, nothing scientific, just doubts in my mind.
I came to this conclusion after my experience with my other reps where sapphire never showed this problem.
I'll buy a cheap diamond tester on ebay to make it sure. Then I'll strip the AR by myself, without too much hesitation, if sapphire is confirmed.
The only case where the water drop test failed for me was my Asian SFSO, supposed to have mineral. Which always made me doubt that the difference was on the paper, to "help" buyers going for the more expensive one. And with its 5mm thick crystal it never showed distortion.
Even if not correct from the replication point of view, I want to go for a CT double AR, to really enjoy the blackness of the dial. At least I don't want this (too) blue tint anymore.