I was (and am) very happy about hitting upon that phrasal adjective, which, as far as I could tell, had never been applied to the Blackwing pencil. (And then borrowed without attribution by California Cedar.)
“Unlike, say, campus, prius is a Latin adjective and adverb, not a noun. And Prius is not a Latin word; it’s the name of a car. Priuses makes better sense to the eye and ear, at least to my eye and ear.”