Cory's purples are (were) the real thing, at least according to Chief and Dino (Cory's source), who are possibly the best fish sellers in the country.
They, in turn, got the purple Moscows from a very reputable dealer, and have been breeding them.
Unfortunately, I think Cory is currently out of purple Moscows. I don't know if he's kept a breeding group or not. The only reason I know this is that he sold me his last trio recently.
If Cory is, indeed, out, you could check out the Fishhouse Blog (in the blog section on the main page of the forum). Look for the Available Stock thread. That's Chief and Dino's sale section. I know they've been selling some fancy guppies this summer.
(Ninja'd by one of the sources. Oh well, I'm going to leave this up to back up his reputation.

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