I came across this etch in Toohey's Black Glass book, page 33. You need a bright light and a magnifying glass to make it out, but it is the same on the three items.
Measell also references these items in his book on page 147, with a note that "Some No. 34 (Addie) cups were decorated with a plate etching (see Toohey's Collectors Guide to Black Glass, p. 33), but this was done at the New Martinsville plant."
