This is not so much a question as an answer to one.

As some may recall, the Ballantine editions from 1965–1981 of the volumes of The Lord of the Rings contain maps which are unsigned and uncredited: the general map of the northwest of Middle-earth, and the Gondor map, both two-page spreads, and the single-page map of the Shire. They're characterized by what one might call exuberant lettering and a lack of cartographic detail.

I wondered if one (i.e., I) might track down the artist by that particular lettering, and so spent some time looking through the lettering of various artists associated with Ballantine Books in the mid-1960s, namely, Richard M. Powers (something of a legendary artist of the time, who worked largely for Ballantine until 1966), Jack Gaughan (who did the cover illustrations for the Ace Books LR volumes, as well as some covers on-and-off for Ballantine), and Barbara Remington, artist of the initial Hobbit and LR volumes' illustrations for Ballantine. It is perhaps unsurprising that I found the uncredited artist of these maps to be Barbara Remington. Comparing the lettering on the maps with that of her larger 'Map of Middle-earth' poster (amusingly, the original $1.49 copies now sell for thousands of dollars), and with the lettering in her book Boat (Doubleday, 1975), the similarites are too many to dismiss. In hindsight, it seems obvious, with her having done the cover illustrations. These maps, I would suggest, provide additional testimony to the rush in which the books were produced: even the borders are hand-drawn, seemingly in a rush, as they are all but straight. How long does it take to pick up a ruler? Too long for that situation, apparently.

Anyhow, 'problem' solved! It was an interesting investigation, if not thrillingly revelatory.