What are the locations of the messages, the cyphers, and their translations?

I only managed to find 3 coded messages (but only 2 cyphers, so I didn't translate one), are there more?

What are the locations of the messages, and their respective cyphers?

What are the translations of those messages? What do they mean? Do they have some impact in-game or are they just lore?

Solution 1:

There are three:

The first code book is in the Soldier's Field gift shop, in the cannon in the central area. This book decodes a code in the bathroom of the restaurant across the street. The decoded message is "Tip the hat to the Vox" and refers to a hat rack in the bathroom next to the one where you find the code.

Behind the hidden wall is a secret room with an Infusion, a Voxophone, and some assorted weapons including an RPG.

The second code book is in the Good Times Club lockup, in the room where there is a large fire and some books being burned. The code unlocks a safe hidden behind a clock in the Plaza of Zeal area. In order to get into this room, you'll have to pick a lock that requires 1 pick. The code reads "The broken clock tolls at midnight" and refers to a clock on the wall to the right of where Elizabeth stands when she reads the message.

Inside is an Infusion, a Voxophone, some lockpicks, and a volley gun.

The third code book is in the basement of Hudson's clothing store, a shop near the Bank of the Prophet. It unlocks a hidden room in the basement of the Bank of the Prophet. The translated code is "type three letters to spell the voice" and refers to a trick typewriter on the desk where you find the coded message.

Behind the shelf is another Voxophone, another Infusion, some lockpicks, and a couple of weapons.

IGN has video guides for each of these, and they also include guides to the two locked chests you'll encounter as well.