There are four identical keysets at Piszkéstető Mountain Station for the observers with heavy, cylindrical keychains. Sometimes on of them is at the caretaker's office. On these keyrings, the largest key opens the main doors of the RCC telescope, the Schmidt telescope and the Cassegrain telescope. The one with the rectangular head opens the door of the 40 cm telescope. The green one is for the glass backdoor.
There is another keyring with the keys for the server room and the electrical workshop in the caretaker's office.