"Mystery at Penmarth" oddball?

Back in February, I wrote about the hard-to-find American first edition of Ruth Manning-Sanders' juvenile novel Mystery at Penmarth. That was the 1941 hardcover published by Robert M. McBride, and it came the year after the original 1940 publication by Collins of London.

In cruising around eBay, I have now discovered what appears to be a Mystery at Penmarth curiosity, the cover of which is shown above.

Here is how it's described in the eBay listing: "1940. 288 pages. No dust jacket. This is an ex-Library book. Blue and green pictorial boards. Ex-Library with the usual stamps, stickers, marks and inserts. Contains black and white illustrations. Marks and tanning to endpapers and text block edges. Crisp pages with bold text. Illustrations are clear and bold. Mildly rubbed and marked laminated boards with shelf wear."

Furthermore, the publisher is listed as Collins and the year is 1940. Although, certainly, eBay listing details can be wrong. In fact, I'm somewhat confused, because a copy of Mystery at Penmarth with this exact description is listed on both eBay (shipping from the United Kingdom) and on Amazon (shipping from Florida). So something's fishy.

Setting aside the mystery of what book is for sale and who is selling it, this eBay listing does seem to indicate that this cover exists somewhere, somehow. It looks like a special library binding, designed for more wear and a longer shelf life. That would make it a separate release from the UK or American hardcover. And this library edition might have be issued by McBride, rather than Collins, as the American school library market was probably more robust.

I'm going to try to do some cross-checking and see if this illustration was pulled from the interior of one of those editions, which would be a big clue as to the publisher, since each edition had its own artist.