Given the patch and diary this was found with I believe this was an American officer with the 4th ID, but there are several entries for troops from both sides and I even think I saw some for French troops. Mostly the notes appear to be about troops and their strength, with possibly several entries dedicated to British servicemen with their serial number.
And given the amount of general information about troop strength and similar I think this could have been a fairly high ranking officer. I got the date from a reference in the middle of the book to an article in a 1918 New York Times paper. The American "signatures" as I would like to call them seem to include addresses and various information about them so this officer could have been collecting this for his own personal reasons. They do mostly appear to be in several different types of handwriting so he could have been letting them write this in is book for them. There are also sections of different various topics you would expect an officer to be interested in. In particular I noticed one section where there was an entry showing KIA and WIA with total troop strength. There is another very long written section where he talks about various aspects of an "Infantry Regiment" but it is very hard to read. The billfold part is leather and from Brown, Shipley of London. It is monogrammed on the front, again very hard to decipher Could be just BSCo for Brown Shipley Co. There was a diary and an original 4th ID patch found with this so be sure to check them out on my other listings. Booklet measures 6 1/4 by 3 1/2 closed. Burgundy cover measures 6 1/4 by 31/4 closed. This item is in the category "Collectibles\Militaria\WW I (1914-18)\Original Period Items\United States\Personal, Field Gear". The seller is "laz-e-bid" and is located in this country: US. This item can be shipped worldwide.