achievementsdiablo-3
The Old Keepsake Box contains 8 of the journals needed by Act 1 achievements "A Quick Study" and "Historian of Tristram". Based on the answer at https://gaming.stackexchange.com/a/70084/26911,
it can be found randomly in Old Tristram or The Old Ruins. Is there a quick way to locate the box?
List of Journals:
From this thread:
Start the winter map. It's easiest to turn around and keep driving until you see a raised platform with a house on the right side. Drive past it and turn around. Now boost into the left side of the house.
This video might also be helpful.
Leah has 16 journals. They respawn in the same places in the first three acts, new journals taking the previous journal's place (so get them while you can). You can return to previous chapters if need be.
There are many lore books. You can check your book collection progress from the achievement list (press Y). Leah's journals are listed under Campaign > Acts 1-3 in the "People lore book" achievement.
Best Answer
The quickest way is to start the quest "Legacy Of Cain" and use the waypoint to The Old Ruins. Look for the Old Keepsake Box at the locations marked by red X. Once found or not(it could have spawned at the The Old Tristram Road), leave the game and resume. Repeat until all 6 journals are found.
Update: From further testing, the box appears most often in those 2 locations I've marked. If not found, try looking at the other locations mentioned in Rill's answer.