Can a Mac's part number be determined with a Terminal Command?
Apple Order Numbers -- which also are referred to as Model Numbers, Part Numbers, or Marketing Numbers.
Unfortunately, Order Numbers cannot be found on the hardware itself nor can they be found in the "About This Mac" section of OS X, and this is the primary limitation of the identifier.
Nor can it be determined using Terminal.
Open About this Mac and copy the serial number from there.
Paste that number in the search box on the Look up web page
It will show you the "Order Number" as example Order MQXXXLL/A