Antique Coin

18 on Easy and Normal, 33 on Madhouse (in other spots). The first is inside the Derelict House Footage tape (blue Kitchen drawer, with the tape's Lock Pick); the last is behind the Corrosive panel in the ship's Workers Access Passage 2.

The game's only currency: there is no shop, you spend them on birdcages. On Easy and Normal they are in Zoe's Trailer: Steroids (3), Stabilizer (5) and 44 MAG (9). That adds up to 17: 1 is spare. Madhouse adds 3 cages in the Main Hall (Scorpion Key 3, Iron Defense Coin 7, Assault Coin 8): 35 in total with only 33 coins.

Cages you leave shut reappear once in the Swamp Mine Office (chapter 7), with whatever you already paid: it is the last chance to spend coins. Achievement "Pelicans in Your Pocket". Not a Hero has its own 10 coins and 2 cages.