Estazunti's Medallion Help

"Use to place an additional Restricted Room Card after defeating the Architect"

After defeating the architect, I went to his console to try to use this, but i can't place it anywhere. When and how am I supposed to use this? Has anyone successfully used this Medallion?

Thanks

had the same problem
i just found out u need to place the medallion on the "Architect´s Chamber" before u do the boss

after that the room gets a mark