In the Black Widow's lair, go along the bottom level, then jump up, above and behind the guard on the second level. When the female guard on the third level turns away, jump up and carefully walk behind her until you can reach the springy chair. It should throw you up and left to the door, which is opened by the Key card.
If you have entered it from the tunnel system then you can exit it the same way. if you have entered it from the door you can use the door. if you need to get into the supply room you have to get a job first which means you have to talk to the assistant curator. once you get the job he will give you a key to the supply room. i hope your question was about counterfeit island. also i hope this helped.
Duck past the Security Room when you don't see the shadow on the window blinds. Then hide behind the statues to avoid the lasers as you make your way to the exit at the right side.
Wait until her shadow moves away from the Security Room window, then run across.
Jump on the light hanging above the Scream to catch the theif and wait for the "investigator" with the police.
The keys on Counterfeit Island :The Supply Room - pass the forgery test trainingThe Inspector cottage - from the lady curator (late in the game)The dragon face lock - collect the six picture piecesThe Black Widow's door - you get the key card in the chase
it is located in the black widows lair
you go behind the furniture and statues
Go up into the guarded room. (see related question)
it is in the statue room
Get the paper
Find out for yourself
In the supply room
In the Statue Room.
Go to the far right in the museum and go through the statue room. when you get to the far left go through that door and it is on the end of the hall.
You get it from the museum curator. After you apply for the job and go through training, he gives it to you.
Sneak out and hide behind statues go through the storage room door and you will be by the dock.
In the upper left of the museum.