This is a short guide to Collector Coin locations in The Council. Obviously, spoilers ahead.

Unfortunately the game doesn't provide a maximum value for the number of coins that can be collected, so I don't know if I have found every singe one. I have found a nice round number of 55, so maybe that's all there are.
The list is ordered by area and then by room. So it's more a reference list than a walkthrough.

Thanks to Baka no Kami wo compiled a list of stuff!

Mortimer's office
30 Next to a column on the east side, south of the bookshelfes.
31 On a couch next to the stairs on the north side.
51 In the chest with a motif representing the alchemical symbol of fire.
52 In the chest with a motif representing the alchemical symbol of fire.
53 In the chest with a motif representing the alchemical symbol of fire.
54 In the chest with a motif representing the alchemical symbol of fire.
55 In the chest with a motif representing the alchemical symbol of fire.

Second Floor Hallway
4 On a chair next to the stairs.
5 On the floor next to a chair.
6 On a couch in the sitting area.
7 On the floor next to a wooden pillar.
8 On the floor in a corner next to a chair.
9 On the floor behind a curtain.
10 On a table.
20 On a table next to a candlestick.

Tower room
34 On a table.
35 On the floor in front of a window.

von Wöllner's room
32 Below a couch.
33 On a table.

Adam's room
18 On the floor between some books.

Piaggis's room
43 On a table.
44 On the floor behind the travel cabinet.

De Richet's room
11 On the floor between furniture.
19 Behind the curtain of the western Window.

Godoy's room
41 On a table behind the piano.
42 On the chimney.

Balcony
12 On a table with a tablet and fruits on a stand.
13 On the floor between the door and a chair.

Hillsborrow's room
29 Next to the bathtub.

Bonaparte's room
21 Behind a table on the right from the door.
22 On a dresser.

Peru's room
17 On the sideboard left to the door between a candle and books.

Great Hall of Zeus
3 On the floor next to a chair.
14 On the floor next to the last chair.

Small Salon
15 On a table in a corner.
16 On the floor left of the long sideboard.

Dining Hall
23 Next to a column at the table.
24 Behind a curtain.

Library
25 Between some books on the floor next to a ladder.

Portrait Gallery
26 On a chair in the center sitting area.
27 Behind a curtain next to the left chimney.

Trophy room
28 On one of the cases.

Service Stairs
36 On a couch.

Great Conclave Chamber
39 On a table in a north east niche.
40 On a table in a south east niche.

Forecourt
50 On a pedestal.

Garden
37 On the ground in a dead end.
38 On the groundi n a dead end.

These coins are within the maze. Here is a very, very, very crude map of the maze:

Pier
1 Next to some luggage.
2 Between some planks.

Crypt Entrance
45 On the floor.
46 On a bench.
47 On a bench.
48 Under a bench.
49 On the floor.