1. In a cupboard in the mess hall kitchen
   
2. In the storage room(where you get the gas mask) on top of the shelf in the far left corner as you enter
   
3. In the infirmary on the vent above the entrance
   
4. In the locker room near the infirmary(head out of the infirmary, go around small wall bit in front of you, through the door, it's on the right) under the bench
   
5. In the library, above the door leading to the caves
   
6. On the scaffolding in the caves, climb the last ladder, can't miss it
   
7. At the top of the stairs leading down to the kennels there's a small room on the right, it's in there in the bin
   
8. In the kennels, inside the left kennel
   
9. In the research room where amabel is, in the toilets next to the right hand wall
   
10. In the chemical lab, in the bottom desk drawer

After the end of the game, you will get a code xor451 that you could use to play schmup.exe (research room)
Go to the game istallation folder\Penumbra Black Plague\redist and find an archive "super_secret" and use the same code.