An authenticity report commissioned by San Francisco’s Mexican Museumfound that 1,917 of the 2,000 pre-Hispanic artifacts from its permanent collection examined are either forgeries or more recent decorative objects, according to the San Francisco Chronicle. “I was shocked,” Andrew Kluger, the chair of the museum’s board of trustees, told Mission Local, which broke the news.

The report was carried out by Eduardo Pérez de Heredia Puente from the National Institute of Anthropology and History in Mexico City and submitted to the Mexican Museum board late last month. Just 83 of the 2,000 artifacts, all of which were previously believed to date from the pre-Hispanic era, were said to be of museum quality. Among the rest, the report found “a good number of modern workshop ceramics, imitating the archaeological ones … from bad to good copies, including some good and high-end forgeries,” according to Mission Local.