The Sea Fairies was L. Frank Baum's attempt to start a new fantasy series after the success of the first six Oz books. The book was handsomely produced by Reilly & Britton, once again using a gold background on the cover label, and metallic inks on the borders of the interior color plates. I like the use of sea green and coral for the cover colors, which ties in nicely with the watery theme of the book, but somehow this doesn't give the same lush impression that the Emerald City of Oz achieved.
The cover label is printed on a textured paper, which seems to deaden the metallic effect - it also made the label prone to rubbing and wear. The color plates are from watercolors by John R. Neill, but this time they are duotones rather than full color, and printed at a smaller size within the large metallic borders. I think full color would have been a much better choice. The overall look of the book is very elegant, but I don't think it's very appealing to a child audience.
The cover did change rather quickly - perhaps the rubbing problem was noticed, or dropping the gold was a cost cutting device. Or maybe they thought a new cover would sell more books. At any rate, just as the new cover label for Emerald City was simply a rehash of an earlier endpaper design, the new cover for The Sea Fairies was an adaptation of a color plate from within the book.
Eventually a third cover was used, this one from a new watercolor by Neill.
I know that some original color plate art survives from this book, but do not know of any black & white pieces.