How to understand if a customer mac is retina display?
The only Model that came with the following graphics card: NVIDIA GeForce GT 330M 256 MB graphics were the Mid-2010 Macbook Pro's (Non-Retina):

"Core i5" 2.4 15" (Mid-2010)


256 MB NVIDIA GeForce GT 330M 
256 MB Intel HD Graphics*


"Core i5" 2.53 15" (Mid-2010)


256 MB NVIDIA GeForce GT 330M
256 MB Intel HD Graphics*


"Core i7" 2.66 15" (Mid-2010)


512 MB NVIDIA GeForce GT 330M  
256 MB Intel HD Graphics*


"Core i5" 2.53 17" (Mid-2010)


512 MB NVIDIA GeForce GT 330M 
256 MB Intel HD Graphics*


You can check the following link for a complete list: http://www.everymac.com/systems/apple/macbook_pro/macbook-pro-unibody-faq/macbook-pro-unibody-video-processor-types-nvidia-dedicated-integrated.html