Whistler etchings are identified by "G" numbers as assigned in "James McNeill Whistler: The Etchings, a catalogue raisonne," by Margaret F. McDonald, Grischka Petri, Meg Hausberg, and Joanna Meacock (University of Glasgow, 2012), http://etchings.arts.gla.ac.uk. This print is G187 state 3 of 3.