After Otto Frank had moved to Switzerland in 1952, Johannes Kleiman once again became managing director of Opekta. In 1955, Opekta and Gies & Co moved to other buildings in the city. By then, people from different parts of the world were already interested in visiting the Secret Annex where Anne Frank had lived in hiding.
Whenever people asked him to, Kleiman returned to the empty building on Prinsengracht to give visitors a tour of the hiding place.