Antique Coin Locations
1. Inside a kitchen drawer, eventually. First you have to play the 'Derelict House' footage (walkthrough here). When you return to the the present, the drawer you lockpicked in the past will now be open, revealing the coin.
2. When you escape the kitchen area through the hatch, watch for a riding mower with an coin on its cowl.
3. In the Main Hall of the Main House, in the drawer of an endtable with an angel on top.
4. In the Rec Room of the main house, on top of a tall cabinet along with a bobblehead in a basket.
5. In the Main House Bathroom, which is on the second floor, past the Rec Room, and roughly above the the garage entrance. Grab this one from the toilet (and think about washing your hands with a First Aid Med, just on general principle).
6. After you've solved the shadow puzzle in the main hall, you'll pass through a room full of hunting trophies, then into a room with some papers and card table. The coin is in the ashtray.
7. In the depths of the processing area, the moment you get the Processing Area map look left. Near a wooden pallet leaning against the wall is a small hollow with this coin.
8. As you leave the house, go down the steps and hang a hard right to search the shrubbery for this urn-based coin.
9. Inside Zoe's Trailer, right in front of the caged Magnum.
10. In a tunnel leading down to the room with a spidery Stone Statuette, on a metal cart.
11. Another toiletcoin, this one on the tank of the disarded toilet in the same shack where you find the Crow Key.
12. In the room with the lantern-weighing puzzle, there's a skinny chest of drawers in the corner, and the coin is in the top drawer.
13. In small room with many bombs, just before entering a large, open area of the barn proper (the same room with the steroid in the locker). It's in a green drawer to the left.
14. Just past the charred corpse with the note, you'll enter a hall with some shelves to your right. The coin is on the second shelf.
15. Down the hatch two workers are talking about in a flashback, bear left and then, when the tunnel branches, go right. The coin is in a dead end here.
16. In the room where you have to drop into some standing water, search the area to your left before climbing the ladder out. The coin is hidden invisibly in the murk here.
17. In a red locked box in the laptop room on the third floor of the ship. You'll need a lockpick to get it and there's only one aboard ship- in the rusty shaft which also contains one of the bobbleheads (accessible from 2F, look in the top right corner of your map, it's the room with the tiny ladder icon. Climb up that very ladder to find the pick in a red metal box).
18. In level S2, as you leave the room with the spiral stairs, Corrosive open the lockbox to claim the last coin of the game (at least until you play Madhouse).