There's only one revision for the entire P8Z77 family, but there are a number of subtypes like P8Z77-V Pro and P8Z77-V LK, so maybe you're seeing one of those. Otherwise I don't know what to tell you assuming we're talking about reputable sellers. You'll always find deals that are too good to be true if you're including fly by night type operations, or places which may be rather lax in correctly labeling used parts as used, etc.