Many of the books that make up the Cherrycroft Series #61 (http://henryaltemus.com/series/series61.htm) were previously part of Series #56-The Boys and Girls Booklovers Series (http://henryaltemus.com/series/series56.htm). Without the jacket it can be hard but not impossible to distinguish them.

The Cherrycroft books are slightly smaller. 6.75 x 4.5 versus 7 x 4.75. So measure carefully.

With a dust jacket several points can help. The later dust jackets have color whereas the earlier do not. The Boys and Girls Booklovers books do not have color on their jackets.
The back of the jacket of the Cherrycroft books frequently have the Little Men and Women Series (#125). This series was published starting in 1907 but by looking at the ads and seeing which books were part of the series, dating your book and assigning it to a series should be easy.

Below are pictures of the Cherrycroft and Boys and Girls Booklovers’ editions of Sonny Boy. Note the added decoration on the latter series’ book. Note also the color on the dust jacket of the Cherrycroft book.