Frank Dumont
3 appearances across 3 restored issues — every one readable in full, free.
Beadle's Half Dime Library, No. 140 — 1880 “Blue Blazes; or, The Break o' Day Boys of Rocky Bar” · p.1 Read the full issue (16 pages) → 
Beadle's Pocket Library No. 109 — 1886 “The Branded Hand; The Man of Mystery” (serial) · p.2 Read the full issue (32 pages) → 
Beadle's Pocket Library No. 198 — 1887 “Ebony Dan's Mask: The Rival Leagues of the Mines” (serial) · p.2 Read the full issue (32 pages) → Appearances are extracted from each issue's own printed contents page; entries we can't read confidently are withheld rather than guessed.