The GE version with a three-note chord in the 2nd L.H. crotchet is most probably a mistake by the engraver, who saw a note in the small protrusion of this crotchet's stem. Admittedly, notes on ledger lines can be barely visible (or not at all), but in the case of chords, it concerns the outermost notes – Fontana would mark the vast majority of inner notes in a clear manner. The absence of this c1 is strongly supported by the FE (→EE) version, compliant with the text of all sources in three remaining, analogous bars 20, 52 and 60.
Compare the passage in the sources »
category imprint: Graphic ambiguousness; Differences between sources
issues: Inaccuracies in FC
notation: Pitch