On my 39 ford deluxe the battery gauge has an ‘n’ between the H at the top and the C at the bottom. The owners manual doesn’t explain what the N stands for. Is it for normal
Do you mean the temperature gauge? If yes, my '39 pickup has the same and my experience is that is about where the stock thermostats would open (160 I am pretty sure) so yes I would call that an N for normal.
Here is my 39 Merc gauge, as you describe BUT with an "L" for "low" and not a "C" as you describe. "H" for "HIGH" and "N" for "normal" and the needle "should" be "around" the "N" with a slight move toward the "H" as the engine revs up.