The “N” prefix to Apple's model identifier indicates a “replacement device”.
This is the full list of prefix identifiers - and their meaning.
- M – Brand new device, meaning the device was purchased new
- F – Refurbished device, meaning the device has been through refurbishing process
- N – Replacement device, meaning the originally bought device was replaced by this model likely due to a service request
- P – Personalized device with engraving, meaning the device was customized with an engraving on purchase
The model number also encodes the region in which the iPhone was intended for sale. Region coding affects availability of some devices features and functionality.
https://theapplewiki.com/wiki/Model_Regions
"LL" indicates that the iPhone was intended for the USA and Canadian markets - "LL" also being used for some replacement units