I still think the key ring is the best idea.
In Reals of Arcadia there were also several keys with the same name, such as "iron key".
When you interact with a door the game simply assumes you try every key in your posession before telling you either "You opened the door." or "The door is locked."
It is normal that you do not know what a key is good for when you find it.
If a door needs several keys and you got some of them there is a message like:
"You have opened a lock but there are still two locked." or "The door has three locks. You have opened already two of them."
It is not absolutely needed to know what key opens which door. If you have an iron key and a copper key and you open a locked door it is sufficient when the game tells you "You opened the door with a key."
Actually, you don´t need this text. You hear a click and the door opens. Without key you get "The door is locked."
Prof. Dr. Dr. Mad S. Tist
World leading expert of artificial stupidity.
Because there are too many people who work on artificial intelligence already
