Why are there always two Apple part numbers?

[tmcdanel]

I wanted to buy a video adapter for my MBPro and was able to see the model number on the old one: A1307
But looking for it i found it is also called MB572Z/A

I know this is an old question, and apologize i could not find the answer with Google but it seems so stupid, i want to know the answer. There is always the same confusion with Macbook model numbers. There never seems to be a simple consistent clean model number when you are looking for parts. If you look in the system description it gives some ambiguous 9,2 when you need to know A####.. you have to know when it was manufactured.. I am not even sure the model # is written on the case.
Why two Applemodel numbers on parts?
Why all the confusion?

 

[triplelucky]

The “A” number can be a series. The “MB” number can be a specific model within that series.

You can use the “serial number” that is on the bottom of the case to look up exact date info.

 

[tmcdanel]

Why ...

Why aren't MB# & A# shown in the system profile?

What is
Model Identifier: MacBookPro9,2
or whatever, in the profile?

Thank you for removing some confusion. That seems straight up. But some still remains in my density.

 

[simon48]

Why aren't MB# & A# shown in the system profile?

What is
Model Identifier: MacBookPro9,2
or whatever, in the profile?

Thank you for removing some confusion. That seems straight up. But some still remains in my density.

It's major revision, minor revision.