~7 1/4" X ~6 1/4", unpaginated. Suede leather covers, the front is deeply embossed with the title letters in gold. I have found RUISDAEL references, but not about watermarked paper. I seek your help to determine more about that, an' whether this is anything rare or a typical Elbert Hubbard Roycrofter's production. The pages are pristine, but the volume has been poorly treated, an' sun-faded on the back. More pics immediately below. Thanks for lookin'!
There are a few sets of books that I've found on-line that use this paper and they all say that it handmade. Here's one example ... https://www.christies.com/lot/lot-1...k&intobjectid=1908727&from=salessummary&lid=1
The Roycrofters had a big book printing business going. I don't know how rare this is, but they made a lot of books.
Lots of variations of this book by Roycroft out there. A leather cover is a plus. This one sold for $75.00. Sold: Rubaiyat of Omar Khayyam Roycroft 1906 W W Denslow Suede Cover, Ornaments Roycrofters Book - Wonderful Books of Oz