Ok, so I have been using a 2011 MacBook Pro for almost 5 years now and only noticed now that the serial number on the bottom case doesn't match the one displayed in 'About this Mac'. I purchased this computer lightly used from a seller with a good track record, 99.7% feedback rating on eBay. I have never had issues with this computer, any time I have gone into the genius bar, I have always used the serial number that appears from the about this mac section. I checked both serial numbers on Apple's website, both have the verified purchase date check mark and are the same model. The reason I bring this up is cause I was planning to sell this, but not sure if I should try to reach out to the original seller I got this from first for more information or is it no big deal? Also, is there a way to clear personal information from a mac serial number if I sell it? Usually when I bring in my mac, they can load all my details + appointment history simply with the serial number. Can that be removed?