Hunter green multi-lined stacking cup. Most, if not all manufacturers, made variations of this pattern, particularly in the 1930s, 1940s and 1950s. Notice how the body shape facilitates stacking. I have similar or nearly identical cups made by Carr, Sterling, and Walker. The next cup you'll see (#006) is a topmarked example by Walker.

Jackson backstamp with 1955 (E4) date code (N is not part of date code). Though Restaurant China, Volume 2, gives a 1923-1946 date range on this mark, mid-1950s date codes have been found. This error, along with others, is noted on the Restaurant China Errata Page (click here to go to that page).