I guess Nvidia have a pile of parts that were not up to the grade of being a GTX 470 or 480.
http://www.fudzilla.com/content/view/18390/1/
This ties in with the "Custom GTX 480 boards" that seem to be popping up.
http://www.brightsideofnews.com/news...elopments.aspx
You think those "custom 480" boards are really for the 460? Makes way more sense to me.