Locations:
1. Seaville: Talk to the dog.
2. Lagos Cave: Chest to the far right of the boss's location.
3. Hanselar: Chest in the left warehouse.
4. Twilight Forest: Chest to the left side of the exit.
5. South Pendeloque Port: Chest in the left warehouse.
6. Obus Westport: Chest in the left warehouse.
7. Guz Village: Chest near the spring. From the entrance of the village,
go to the left and onto the next screen.
8. Guz Village: Talk to Sassol after the events in the village conclude
(second visit, before Va'Mell Volcano).
9. Anders Mine: In the room with the save point, complete the puzzle
and you'll find the coin in one of the three chests.
10. Straga: Chest outside the military headquarters, to the left of the city.
11. Shoalhaven: Chest in Sumisona's house.
12. Odette Sluice Gate: Chest across the bridge.
13. Lion Park: Chest within the arena.
14. High Tower: Chest on the third floor.
15. Desert Shack: Chest inside the shack outside Schehera Desert.
16D Schehera Desert: Chest in the fourth area,
right after the river of quicksand and to the left of the stairs.
17. Schehera Desert: Chest by the the adventurer in the oasis.
18. Holy City of Prinseur: Chest by the beach.
Go down the winding path outside the Saintex Cathedral.
19. Saintex Cathedral: Chest to the left of the save point before the boss.
20. West Marquis Port: Chest by the left warehouse.
21. Trilliant Port: Warehouse to the left.
22. Layve Village: Speak to the Misty Dog.
23. Layve Village: Chest in Zirconia's house.
24. Obus Southport: Chest in the right warehouse.
25. North Marquis Port: Chest in the left warehouse.
26. Mountain Shelter: Chest inside the shack outside the Mountains of Bremen.
27. Mountains of Bremen: Chest in the second area shack, before the save.
28. Blanche Village: Chest next to a door at the area before the exit.
29. Blanche Village: Talk to the Cloud Sheep next to the shops.
30. Dronning Village: Chest right next to the Shadow Gem.
31. Dronning Village: Talk to the old man at the entrance after the events.
32. Max Castle: Talk to a soldier standing by a bookcase
to the left of the main entrance.
33. Cind'rella: Chest in Lithea's room.
34. Rapunzel: Chest to the right side of the second floor,
where the final scene between Hisui and Lithea takes place.
35. Obus Eastport: Chest inside the warehouse.
The following Namcoins can be found in the yellow spots in the world map:
36. Beach near Seaville.
Just go around the hill outside the village and you'll see it.
37. Behind the mountain across Lagos Caves.
Go between the two mountains and approach the cliff.
38. Behind the small hill between Hanselar and the port.
39. Outside the Anders Mine.
Use the exit from the Straga side that leads to Guz.
There are two cliffs at the end of the the road with yellow spots.
The left has a Namcoin.
40. Near the bridge to Straga.
41. East of the Obus eastport, near the beach where the machoman is.
42. Outside Prinseur, right below a hill to the east.
You can't see it when coming from Schehera Desert.
43. Move along the road between Prinseur and West Marquis port
until you see an opening between two mountains. Head north and then west.
44. East from Trilliant port.
45. Head to a small beach northeast of Layve and then north.
46. South of the shelter shack near the Mountains of Bremen.
47. Right outside Dronning.
You will need the airship for these:
48. Near the beach where you get the swimsuit costumes.
49. Small island to the bottom right, southeast of Obus Eastport.
50. Small desert island to the west of the Triverse Gate.
51. Beach to the southeast of Seaville.
52. Near the western Oasis in Schehera Desert.
53. Snowy island formation northeast of Dronning.
The following coins are part of sub-events:
54 - 61: Clear the Single Arena matches with all characters.
62 - 66: Clear the Extar Courses in the Arena.
67: Duck Boat
68: Beast Talons
69: Secret Base
70: Letter Delivery
71: Fragments of the Black Moon
72: The Crying girl's Voice
73: Forbidden History Book
74: Aifread's Treasure
75: Beach cave
76: Ultra Marine's Past
Source Gamefaq