I've got multiples of several keys -- like 2 Chrome keys, 3 Iron keys, etc. Is each kind of key the same and I've just got some duplicates that I can get rid of, or are they distinct keys and I need to keep each copy? Thanks!

The keys are strangelly designed in this game. from a guide I encounterd online:

"When you find a key in a certain level, it will usually
unlock a grate somewhere on that level. You will not be allow to
drop it before it unlock anything. If your character carry too
many keys in his back, he might not be able unlock the grate
even though he is carrying the correct key. If possible, don't
let any character carry too many keys. So it is advisable to
store the key in the cache in the sanctuaries after it was used."



Not completely sure about this but I must understand that each key is valid only once, normally for a door from the same level. You cannot drop a key that you have not used yet, so it can be a way to make things safer. A clue, probably.
But as it is said above, if a character carry too many keys in his/her inventory you could not be able to unlock the respective door (a bug probably?).

So I must understand that when a key has been used you could drop it into your sanctuary box safely.

Geetings