Title: Keep your hair on Johnny shows publication date "ca. 1882," while Title: What A Wonderful Difference It Makes shows "ca 1885," consistent with the "period of activity" indicated above.

Both of these two indicate "John Cooke, Vincent Davies," so a search for Davies, or one of the others in Malcolm's list, might show an additional collaboration. The first one indicates "W&M.," which I believe identifies a publisher.

John