Unfortunately, Tom, I believe the worth of your copy is comparable to the others you have found. One reason for believing so is that a great number of different, classic children's books published by M. A. Donohue in this era are also valued around $10.
M. A. Donohue was a mass publishing house, not necessarily known for the quality of its printing -- which is perhaps the reason that such antique books have such a surprisingly low value.
Here is an excerpt
from a collegiate conference on publishing house history, by Karen Crossley: "In the early 1900s, the M. A. Donohue publishing company of Chicago began publishing a series of Black Beauty for Young Folks
editions. So many of these slim, large format volumes were published, differing only in the cover illustration,
that it's hard to imagine that any American nursery at the turn of the century would have been considered complete without one. The books all have attractive covers, but inside they are very dull affairs, printed on cheap paper and illustrated with a variety of muddy halftone prints seemingly chosen for inclusion because they
feature horses, not necessarily because they illustrate any scenes from the text." (bolding mine)
She also notes that the first American edition of Black Beauty was a pirated edition adapted by George Angell. Thus, your book is probably one of the many referred to in the excerpt; while it may not match the other books you have found online perfectly, it is almost certainly from the same series and of comparable worth.
I hope this further information helps, though I'm sure it's not the answer you were hoping to receive. I'm happy to keep researching, so just reply if you have any questions.