The museum grew quickly. After its inauguration, it moved to a building on Jalan Taman Mayangkara, then expanded again to a larger space on Jalan Simpang 3 -- now Jalan Pemuda 3 -- where it acquired an exhibition room, a library, offices, and an auditorium. Surabayans came to know it simply as Museum von Faber. Then came the Japanese occupation, and the museum closed for nine months. It reopened, but von Faber's world had changed irreversibly. The Dutch East Indies became Indonesia. Colonial institutions lost their patrons. When von Faber died on September 30, 1955, the museum lost not just its founder but its driving purpose. Management fell to a cultural foundation, the Yayasan Pendidikan Umum dan Kebudayaan, but without von Faber's obsessive stewardship, collections were damaged and looted. Pieces of Surabaya's history, carefully gathered over three decades, scattered back into the city that produced them.

The museum might have disappeared entirely if not for a series of institutional rescues. In 1964, Professor M. Soetopo donated funds to keep the foundation afloat. Then the national government stepped in. On May 23, 1972, the museum reopened under a new Indonesian name: Museum Jawa Timur, the East Java Museum. Two years later, on February 13, 1974, it was formally designated a Museum Negeri -- a state museum -- giving it government funding and official protection for the first time. The inauguration ceremony, held on November 1, 1974, marked the moment when R. Banu Iskandar, head of the cultural foundation, handed the museum's management to Ida Bagus Mantra, the General Director of Culture. A German collector's private obsession had become a public institution of the Indonesian republic.

With state status came a new name: Mpu Tantular, after the 14th-century Javanese poet who served in the court of King Hayam Wuruk during the golden age of the Majapahit Empire. The choice was deliberate and resonant. Mpu Tantular authored the Kakawin Sutasoma, a Buddhist poem that contains the phrase Bhinneka Tunggal Ika -- Unity in Diversity -- which Indonesia adopted as its national motto. The poet's name means, roughly, "the one who is not easily swayed," and his great work argued for tolerance between Hinduism and Buddhism at a time when both competed for royal patronage. Naming a museum after him -- a museum founded by a German, sustained by a Dutch colonial government, rescued by an Indonesian republic -- layered the institution with exactly the kind of meaning Mpu Tantular would have appreciated: different origins, one purpose.

The museum has moved four times since its founding, each relocation reflecting a shift in its identity. From the Town Hall to Jalan Taman Mayangkara, to Jalan Pemuda, back to Taman Mayangkara in 1975 (inaugurated by Governor Sunandar Priyosudarmo on August 12, 1977), and finally, on May 14, 2004, to its current home on Jalan Raya Buduran in Sidoarjo. Today, the museum houses over 1,500 items organized across ten thematic categories: prehistoric artifacts, Hindu-Buddhist relics, Islamic-era objects, colonial-period documents, ethnographic collections, ceramics, coins, manuscripts, and more. The collection spans the full arc of East Javanese civilization, from stone tools chipped by hands that never imagined agriculture to photographs snapped by a German who could not stop documenting a city he loved. Von Faber's original photographs are still among the holdings -- the seed collection that grew into a state museum, moved four times, and outlasted every institution that tried to own it.