Refer to the descriptions and video(s) below on how to find all items that you can inspect in the game. You don't need to reach the next checkpoint to save your progress. As long as you inspected the item, you can immediately quit to the main menu without finishing the checkpoint or chapter. These are divided to individual checkpoints per chapter for your convenience, in case you need to do some backtracking for anything you missed.
Checkpoint: Rules of Engagement
1. Object #6
Checkpoint: Commandeered
2.Phonograph Cylinder #6: Agamemnon Christening
3. Newspaper #5
Checkpoint: CQD, SOS, DE, GFAXX
4. Phonograph Cylinder #7: Evacuation Procedures
After the cutscene where the prominent figures have evacuated via emergency gondolas, follow Perceval until you reach the armory. This phonograph cylinder is found outside the locked armory, on the table.
5. Document #10
Disable the electronic lock and inspect this document on the table inside the armory itself
6. Item #10
After stocking your arsenal in the armory, proceed to the next room to find a corpse. Examine it.
Checkpoint: Divided
7. Photograph #4