I'm Curious about my iPhone Model Number

Hello Support Community,

I am the owner of a factory unlocked / SIM-free Space Grey 64GB iPhone 6, model A1586. Maybe you can satisfy the curiosity I have about my iPhone's model number that google returns a "your search - ng4f2ll/a - did not match any documents" when I tried to search it on google.

My model number should be "MG4F2LL/A" but when I got to "Settings > General > About > Model" my phone is shown as "NG4F2LL/A"

I was wondering why my phone's model starts with an "N" rather than a "M?"

I know it's a very small detail that I should overlook, but I'm just curious. I've sort of become an Apple Product junkie and this quirk about my phone makes me wonder, what's the difference?

Everymac.com says that my specific phone (Global/Sprint/A1586) should be a "MG4F2LL/A" but it isn't.

"The factory unlocked models in the US with 16 GB, 64 GB, and 128 GB of storage, respectively, are MG482LL/A, MG4H2LL/A, and MG4C2LL/A in silver; MG492LL/A, MG4J2LL/A, and MG4E2LL/A in gold; and MG472LL/A, MG4F2LL/A, and MG4A2LL/A in "space" gray."

Any hardcore Apple junkies or someone else have an idea or clue as to the difference? What makes "n" different from "m?"

I'm curious to know. Thanks everyone!