Thank you all for your comments and references. I am going back to my Gaskell and Carter before I finish the record, to see what they have to say.
Eric and Robert, I found the large paper idea would make sense for a presentation copy, except that the text is not centred, it is close to the spine and up in the top left corner, as it would be if bound as a smaller volume. So the margins are by no means aesthetically proportioned. Also the pages are roughly the same size but in many cases there are 2-3 cm difference.
Thank you Patrick for giving me some ideas about phraseology, that is very helpful.
I really appreciate all the assistance. There are many notes to make. In addition to the initial provenance, the book is ex libris Richard C Jackson, Fellow of the Royal Historical Society, and bears his elaborate bookplate. The binding is also curious. It is brown cloth, but has bevelled edges as one would have seen in much earlier bindings with wooden boards. The spine and left board have been stamped with the title, etc. consistent with the other copy we hold, although that cloth is a wine colour, than brown. I wonder if they had the boards spare and as a quick binding on the textblock to be sent courtesy of the author, the publisher improvised. With the cloth stamped with a quite elaborate central ornament incorporating the initials of Michelangelo and Raphael, the same as the other copy we have, would suggest that it was not a personal binding but one undertaken by the publisher. But I won't bore you with any more curiousities.
