This ten book series is similar to the Wee Books for Wee Folks Series. See http://henryaltemus.com/series/series186.htm
The small books (5.5 x 4.25) have grey cloth with a 2.5 x 3.5 book appropriate color illustration as a paste-on (applique).

All the books have dust jackets. The book shown below is book #4 (The Old, Old Story of Poor Cock Robin). With the addition of this jacket picture, nine of the ten books in the data base are jacketed.
The tenth, The Story of Chicken Little, is shown without its jacket. See http://henryaltemus.com/series/series188.htm