I was recalling the county prefixes of NH license plates from my childhood. From about 1956-76 you could tell where in NH someone was from by the first two letters on their plates.
Manchester, or more likely all of Hillsborough County, had the H's and I's, at least. I think Merrimack County had the M's, Rockingham the R's, and I think Sullivan County the S's. How they beat out the more populous Strafford County for that I don't know. I had a friend from Coos County whose plates began "OA," but I'm not recalling much more and can't find much on the net. I wish I'd paid more attention then.
With the telephone codes, you at least still have the numbers to give you a clue. Manchester's 62 numbers were NAtional, Goffstown was HYacinth, and Westford MA was MYrtle. But I'd like to know those plate ID's again. I could probably build up my repertoire by looking at old photos that have cars in them.
But if any of you know some, I'd be obliged.