A Publisher's Foreword dated "Kigen 2600"¹ (1940) was added to the second set of prints and released with the first four prints of Set Two in January 1940.

The title for each print is provided in three places: affixed to the back of the paper the print was originally tipped to, on the colophons attached to each envelope the prints were released in, and in the Table of Contents that accompanied each of the two sets. Note that I have not seen a table of contents for Set One², though it likely exists somewhere since Keyes states that a table of contents for Set One was released in April 1937.³

The size of the original edition for both sets was likely between 100 and 300 copies.⁴ While both Hillier and Keyes state that only a single edition of the series was made (based on Unsōdō's reports that the blocks were destroyed when their Tokyo facility was bombed during WWII), at least six of the prints were reissued by Unsōdō after Seihō's death, as square format (shikishiban) prints mounted on decorative cardboard. Yanaka Pagoda in Moonlight in this collection is one of the reissued prints; and other Unsōdō reissues include Early Summer, Narcissus, Green Bamboo and Small Bird, Puppy and Crimson Camellia. Given Hillier's and Keyes' assertions, I have to assume that the re-issued prints were made from newly cut blocks.

The majority of the prints were produced using traditional woodblock techniques, but collotype (yamato-ban insatsu)⁵ , a photographic process, was used for seven prints in Set One, which reproduce existing paintings by the artist.  Hillier restates Unsōdō's assertion that "Seihō himself supervised the printing, which was carried out by one master printer."⁶  Keyes identifies that printer as Shinmi Saburō 新味 三朗⁷, Unsōdō's primary printer for many years.

¹ Kigen 2600 references the 2600th year of the Imperial Era (1940 AD) and was an occasion for great nationalist displays in wartime Japan.
² A table of contents for Set One was not present in the New York Public Library's Spencer Collection when I viewed it in 2012 and 2013.
³ Ehon: The Artist and the Book in Japan, Roger S. Keyes, The University of Washington Press with New York Public Library, December 2006, p. 289.
⁴ Hillier in The Art of the Japanese Book, p. 993, deduces, based on the "normal practice" of the publisher Unsōdō, that no more than one hundred copies of the first ten parts were printed. Keyes, however, notes in the "Bibliographic Descriptions and References" section, p. 289, of Ehon: The Artist and the Book in Japan, "Edition of 300" and the last two colophons appearing on the envelopes for set two, state  "三00部" (300 copies).  At the time of his writing in 1987, Hillier did not find evidence that any of the second set of prints were ever produced. Of course we now know that the second set was issued and, in fact, is present in the New York Public Library's Spencer Collection.
⁵ Collotype printing had its first commercial use in Japan in 1889.  The collotype process was versatile and could produce high quality images on different types of paper. Collotype prints can be readily identified by the presence of image reticulation, a product of the finely cracked gelatin plate used to print the image, which can be seen under magnification. The size of the reticulation varies from print to print, but cannot be seen by the naked eye. The image can be a variety of colors.  Prints made from collotype plates can be either hand printed or printed using a press.
⁶ The Art of the Japanese Book, Jack Hillier, Sothebys Publications, London, 1987, p. 993.
⁷ Ehon: The Artist and the Book in Japan, Roger S. Keyes, The University of Washington Press with New York Public Library, December 2006, p. 252.

Seihō’s Masterworks - an elegy and a testament

I had the opportunity to view and photograph all sixty-six prints that make up the two sets of Seihō's Masterpieces in the New York Public Library's Print Room (part of their Spencer Collection¹), and they are as impressive as Roger Keyes' comments, below, indicate. 

In attempting to translate the titles of the prints into English (and all errors in translation are mine alone), I found it intriguing that many of the titles used uniquely Chinese characters, suggesting a rather cultured market for this series. I also enjoyed the rather allusive nature of some of the titles, such as 殘夢 (Remnant of a Dream), picturing a fox and a noblewoman's sedge hat. A Japanese friend suggested that perhaps the fox, which can take on human form in Japanese legend, is vaguely recalling her past form as a noblewoman - the presence of the sedge hat triggering that "fragment" or "remnant" of a vague memory of things past.

The Comments of Roger Keyes
Source: Ehon: The Artist and the Book in Japan, Roger S. Keyes, The University of Washington Press with New York Public Library, December 2006, p. 252-253.

¹ The Spencer Collection surveys the illustrated word and book bindings of all periods and all countries and cultures, from medieval manuscripts, Japanese scrolls, and Indian miniatures to monuments in Renaissance printing, illustration and binding to contemporary livres d'artistes. 
http://www.nypl.org/locations/schwarzman/prints-and-photographs-study-room/spencer-collection
² While Keyes references "sixty-three representative pictures," a total of sixty-six prints were issued in the two sets of Seihō's Masterpieces.