"(Totally incidentally, a few feet to my left as I type, is a low-cut, leather 3-pin boot with fur-out, sheep-skin side-lining, white nylon laces, and no trace of a brand name remaining, except it is stamped "made in Norway" on the bottom. I love 'em.)"
That's exactly what boots I started skiing in for 1978-1979.
The 3-pin toe was offered in three pin-width sizes, 71mm, 75mm, and 79mm. Even though 75mm became standardized, mine were 79mm. Of course that brought up a whole set of compatibility issues later on.