A notebook of this style though would not likely have decorative endpapers, but something rather plain, I would think. It's basically a ledger, after all.
i used March 31 1936 as Abner's last entry according to the time line was March 30th 1936 so he sent it the next day so it was sent a few weeks before Indy had the visit from Major Eaton and Col Musgrove.
According the the lost journal of Indiana Jones the Ravenwood diary was sent to him in 1925 to convince him that it was worth going on a dig with him but directing him to travel by a devious route whose end point was I assume Egypt. Patan in Nepal is where Ravenwood had his bar we see in Raiders. However I've read elsewhere that Indy didn't actually know where it was until he worked out its location in Ravenwood's journal before going to find Marion at the beginning of the film. Not the first time I've found time-lines mixed up in the Indy story.
I'm having a fresh go at a Ravenwood journal using a Magnoli book as a basis. The current plan is to do up to 1925 as Ravenwood and his researches when Indy joins him on a dig near modern Tanis and they find the headstaff. Indy keeps the journal from this point onwards and adds the finds from the Egypt dig and his own notes after Raiders and actually finding the ark.