CHARLES KELLER Rare signed lithograph, an early labor piece (undated), entitled "High Air to Low ", with Keller's social conscience on full display, combining strong dark brush strokes, charcoal and dry point to grimly depict the plight of four exhausted mineshaft workers of mixed race. Approximately 16" x 11 1/2", clearly signed, titled, & editioned "25 proofs" in pencil in the margin under the image. Top edge ragged, one vertical crease visible at right, neglible folds, otherwise suitable for framing. $300-400