Steve, I am glad to know that "older traditional singers not affected by Tin Pan Alley and the folk scene learnt the great majority of their songs in their youth." This would tend to push a bunch of possible references back into an earlier period. I also appreciate your second suggestion.
The Northern Pennsylvania version of "Barbara Allen" above, from the singing of Walter S. Chatham, is very close to Child's B version:
a. Roxburghe Ballads, II, 25; reprint of the Ballad Society, III, 433. b. Roxburghe Ballads, III, 522. c. A broadside formerly belonging to Bishop Percy. d. Percy's Reliques, 1765, III, 125.
It has obviously been somewhat localized but is recognizably the same ballad. So did that "broadside formerly belonging to Bishop Percy" somehow find its way to Northern Pennsylvania, or did Percy's Reliques end up there. Or had this version remained in the oral tradition. All rhetorical questions, but interesting to wonder about.