Hi Flashdrive
I hope I haven't ruffled any feathers as it certainly wasn't my intention. I won't bother with any more posts and wish you well with your search for a well priced M90.
The only thing I am left wondering about is if you already knew everything I mentioned you therefore knew the description from the advertisement is not actually correct - so why bother repeating it.
Anyhow - peace and clear skys.
PS
You are absolutely correct "real" flourite is very expensive but, once again, to dispell another conveyed myth - flourite is not any more brittle or prone to degradation etc than any other glass - this is another piece of folklore that seems to have come up out of the marketting to shift people towards being more comfortable in buying FPL OTAs over the more difficult to produce and therefore more expensive flourite lens wherein the profit margin for the manufacturer is likely to be that much smaller.
Anyhow cheers and good luck with finding the Megrez 90