This series was published from 1915 until Altemus stopped publishing.
In 1931 Little Black Sambo was added to the three book series. The new book for the database is 8.5 by 6.25.
The front cover has an applique on its entirety. This is the second Black Sambo I have seen in this series. The other is slightly smaller (8.25 x 6.25) and has a cloth cover. It is also shown below.

Both of these books were copyrighted by Howard E. Altemus in 1931. There is a David McKay published reprint of this book which was published after 1935. It has the same format as the Altemus book with the applique cover but is 8.75 x 6.25. That may mean that the cloth book below preceded the applique Altemus book.

There is a dealer (who shall remain nameless) who insists his David McKay copy of Little Black Sambo is the first “large size copy” of this title. “RARE FIRST LARGE EDITION PRINTING, after original American small format edition from Altemus Publishing”. Presently he is listing this copy for $200+ on Ebay. He has been presented with information about the earlier large Altemus books but chooses to ignore it. Hopefully no uninformed buyer will purchase his overpriced reprint.