@ ravishingrick: ugh, actually jimmyzfu's was the only one I did not try on my own. I was speaking on what I heard from other members' experiences. On what you say, now I wonder whether they were including jimmy's crystals in those experiences.
On the other hand, the crystal I got from exclusive_discount_uk along with their case is a gorgeous one, thick, and AR coated. Even my watchsmith (who is fitting the new sapphire cyclops on it to reassemble my 028A) complimented about it. I have not it in my hand right now (I should have it again tomorrow), but I am quite positive it was 35.5 mm.
@ kritz: stay away from x-jewelry! Even better, do a search here and look.
I am going to file a dispute on them, or to leave a negative feedback at least, as soon as I'll be done with the mail exchanging with them about the issue.
From them I got a class crystal (tested with 4 different tests, including thermal conductivity and electrical conductivity with proper tools), thin, and even low-quality as a glass (lots of whitish inclusions). Barely usable even as a glass crystal.
And yes, it was advertised as sapphire.
Btw: even the advertised gasket was missing.