An upcoming special exhibition at the National Palace Museum Southern Branch is to feature 13 antique pottery pieces from the Northern Song Dynasty known as ru ware  , which it said experts consider the “rarest of rarities.”

While 300 pottery items are to be on display, the ru ware created for the imperial court would be the most eye-catching, said Weng Yu-wen , an assistant researcher at the museum’s southern branch and the planner of the exhibition.

Only 21 objects in the museum’s pottery collection of 25,000 items are ru ware, which are usually displayed individually as the centerpiece of an exhibit, she said on Sunday, adding that the museum has not arranged so many for simultaneous public viewing since the “Grand View” exhibit in 2006.

Previously part of the collection of the Qing Dynasty’s Qianlong emperor, the museum’s ru-ware pieces are marked by unusual size and fine crazing, which resembles an insect’s wings, Weng said, adding that the items to be exhibited are “priceless.”

In 2017, a ru-ware brush-washer dish belonging to United Microelectronics Corp founder Robert Tsao, which is of quality inferior to that of any piece owned by the museum, was auctioned at Sotheby’s Hong Kong for HK$294.3 million (US$37.6 million at the current exchange rate), she said.

About half of the exhibit’s other artifacts would be comprised of other Chinese imperial workshop products from the Song, Ming and Qing dynasties, while the other half would be porcelain from Southeast and Northeast Asia, Weng said.

The exhibit was originally conceived with a pan-Asian focus, she said, but added that the plans were expanded after National Palace Museum Director Wu Mi-cha said that the museum should do more to serve the needs of the nation’s central and southern regions.

The exhibition is to run from Saturday next week to Nov. 1, with the entrance fee waived on weekends and holidays until Aug. 31, the museum said, adding that closing time would be extended to 6pm during the period.