Throughout the Henry III long cross series one often sees the capital letter “H” used for an “N”. This usage is not consistent, in that many coins have a mixture of “H” and “N” in their reverse legends. In this small study I have analysed the proportions of different usages of H/N for several mints and moneyers. This has allowed various conclusions to be made about the die preparation process, and has highlighted some rarer lettering combinations that collectors may wish to look out for. I would very much welcome feedback on the observations and conclusions presented.
Henry III Long Cross Pennies – Analysis of the Use of the Letter “H” for an “N” – Robert Page
BNS Research Blog 
Is it relevant that the capital N used in documents produced by the Exchequer at that time looks like a modern H?
For example, here is the top of the Northamptonshire section of the 1258 pipe roll:
http://aalt.law.uh.edu/AALT4/H3/E372no102/aE372no102fronts/IMG_1530.htm
You will see the heading Norhampton’, and the first line beginning Hugo de Manneby – the N could easily be taken for a modern H.
Thanks for your comment Richard, as well as the interesting image. Using an “H” for an “N” was a clearly a common habit back then, and my paper attempts to address variations in the patterns of usage on Henry III pennies. It would be interesting to know if anyone has ever studied H/N on ancient documents…. though I doubt whether it would yield any significant conclusions. However, with these coins, I suspect the observed variations may be able to tell us something about the die production.