Model of my mobile starts with letter ( N) I want to know is it new iPhone or not

Hi

I want to ask about the model of my mobile it’s start with letter ( N) I want to know is it new iPhone or not because i read its used ones if it’s start with N my phone before this I took it to apple store to fix a problem which was restarting by it self and that model was starting with (M) letter which stands that it’s new as I read so they change it with new iPhone as they said it’s a new one but this model start with (N) so is it new one or no !?

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