I found the author's initials were on a copy of the broadside from the sale catalog of Richard Herber's library, c 1832. A later catalog of the collection published by John Russell Smith left the initials off, so final confirmation came only on the publication of the Euing Collection, 1971 (Euing #377 is the one with the author's initials). H. E. Rollins 'Analytical Index to the Ballad Entries' lists Child ballads in the Index, but he didn't recognize this one as such. Later issues of broadside ballads usually dropped author's initials, which is why I've tried to locate all issues for the broadside ballad index on my website (for that and for finding when a tune is first named).