From the Whistler on-line catalogue raisonne (Glasgow): One impression is on cream laid paper with the splendid watermark of the royal coat of arms and motto 'HONI SOIT QUI MAL Y PENSE', such as this impression. This watermark is seen on another etching of this date, Hurlingham, suggesting they were printed at the same time.
"Little Putney Bridge" was mostly sold through the Fine Art Society after publication in 1879, and in the volume published by Wedmore in 1883.
The main print-run of Little Putney Bridge was for publication in 1883, by which time the butterfly signature had faded badly. The size of this edition is not known. There are over 40 impressions of this final state in public collections. As published by Frederick Wedmore (1844-1921) in 1883, it was usually printed in black ink on wove paper.
Many impressions of the etching as published by the Fine Art Society and later, by Wedmore, were acquired by American collectors, and made their way by gift or bequest to public collections, particularly in America.
Cited from: Margaret F. MacDonald, Grischka Petri, Meg Hausberg, and Joanna Meacock, James McNeill Whistler: The Etchings, a catalogue raisonné, University of Glasgow, 2012, on-line website at http://etchings.arts.gla.ac.uk.