Codes And Combinations In (mostly Order) You Encounter In The Game
First Fountain Gate - 615
Office Area door - FLOWER FEATHER (top row / left, right)
FISHTAIL FLAME (bottom row / left, right)
First Pool Table - 8617
Second Fountain Gate - 326
Overlook Code - 2182
Wood Cabin wall box code - 0147
GraveYard Door - FISHTAIL FEATHER (top row / left, right)
FLAME FLOWER (bottom row / left, right)
Swimming Pool door - 1991
Second Pool table - 5186
There are some real obvious ones (such as Old House 2nd floor left side) that are not here, just the ones that require a round disc - or a little more not right in front of your eyes.
I might update this in the future with pics and more found in game.
Hope these help with speed runs and the SEER achievement!
Source: https://steamcommunity.com/sharedfiles/filedetails/?id=2714080044