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I think you need to look at the hardware tab in the System Profiler. Not sure if the "About This Mac" screen will say i5, i7 or so on. Should ask to see this screen:
5c0voo.png
 
Its not an i5. Seller is trying to dump his old crap for premium. I got an i5 yesterday and it shows i5 in about this mac screen where you see RAM and CPU. This is old C2D. Another give away is that seller is running 10.6.2 OSX not even latest. My Refurb i5 Macbook Pro came with 10.6.3 restore disks
 
If you note the heading it says MacBookPro 17 not i7. That probably refers to the screen size not the processor.

EDIT: Just spotted you said i5 (not i7). hehe my bad. Nothing to see here move along!
 
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