I need an explanation of model numbers

I've noticed that there are 2 different types of model numbers associated with Microsoft items. I need to know how one is located. Microsoft Surface Tablets and Computers appear to have 2 model numbers (Ex. CR5-00001, QWU-00001, V4C-00064). Then they also have a model that us the standard 4 digit number (Ex. 1631, 1769, 1516). Where are the 7 digit model numbers located in the system to identify the item?