I turned on NFC and got no icon on the header. Yesterday morning when I turned on my phone I had a large N, it could be described as one over another, indicating I had the Android 7.1.2 beta waiting for download. Are you a beta tester for Android?
Also might depend on your device. I have NFC turned on on my Nexus 5X but don't show the old "overlapping N" icon, as ptkelly said. I am also in Android Beta, but have never seen an N for that either, just the software update icon.
If you do the two-finger down swipe to get the expanded icon notification and then click on the edit icon you can see the large N icon for the beta program. I don't know what it's for.
"Morke" is correct - I have a Galaxy S7 Active (AT&T) and have NFC (it's that Samsung "Near Field Communication" for transferring files between two Samsung phones by just touching them together Scott) enabled - the Icon Scott asks about showed up as soon as I enabled it AND it was there with Marshmallow and is still there with Nougat!