Gaming Need help completing Unmetal the game

[Archangel22]

Sorry not sure where to post for game discussion or help. Just wondering if anyone has found all 3 secrets in stage 9 for Unmetal? I can find the Zelda reference at the catacombs and to climb down the ladder in the roof by breaking a box. Not sure where the 3rd is. I imagine it's the card key level 5 as that is the only slot left in my inventory. I've done this level so many times and looked everywhere for it