During renovation of the Famen Temple (Famensi 法门寺) in 1987, an underground “palace” was discovered under the foundation of the pagoda. This secret vault was found intact and had never been looted by grave robbers.
Upon opening the vault, the archaeologists discovered remarkable treasures including the relic of a finger bone of the Buddha (释迦牟尼).
Almost overlooked among the many priceless treasures was a set of thirteen coins.
Shown in the image below are the 13 coins made of turtle shell (玳瑁币) which are the first in Chinese history to have been discovered made from this material.
Famen Temple is situated about 75 miles (120 km) west of Xian (西安) in Shaanxi Province (陕西省). It is unclear as to when it was founded but historical records show that the temple had achieved consider size by the time of the Northern Wei dynasty (北魏 386-534 AD). The best historical evidence points to its founding during the middle to late Han dynasty.
In 1981, the thirteen-story octagonal brick pagoda at Famen Temple, which was built in 1609, partially collapsed due to heavy rains.
During renovations in 1987, the foundation of the previous Tang dynasty (唐朝 618-907 AD) wooden pagoda was discovered underneath the foundation of the brick pagoda.
Steps were discovered which led to a lower level.
The archaeology team entered an underground palace by going down this 19-step staircase where they found a door.
The archaeologists opened the door and proceeded along a long narrow path which was paved with a thick layer of coins. There were more than 27,000 coins.
The coins dated from the Tang dynasty and included kaiyuan tongbao (开元通宝) and qianyuan zhongbao (乾元重宝) copper coins.
Included among the priceless royal treasures in the underground palace were the thirteen coins made from the shell of the hawksbill sea turtle (玳瑁).
These turtle shell coins are modeled after, and have the same inscription, as the copper kaiyuan tongbao coins.
The turtle shell coins are 2.75 cm in diameter, 0.06 cm thick and weigh 24.8 grams.
According to the Dharani Samuccaya Sutra (佛说陀罗尼集经):
《佛说陀罗尼集经》中曰：“其七宝者：一金二银三珍珠四珊瑚五玳瑁六水晶七琉璃”.
This tantra states that there are seven “treasures” or precious things: (1) gold, (2) silver, (3) pearl, (4) coral, (5) turtle shell, (6) crystal, (7) colored glaze.
Coins of a precious material like turtle shell would have only been made to commemorate a very special occasion. In this case, they would have been made by order of an emperor to honor a sacred relic of the Buddha.
There is no mention of coins made of turtle shell in any ancient Chinese historical text so this discovery came as a complete surprise to Chinese archaeologists and numismatists.
As to why there are 13 coins, experts say that the number “13” is considered auspicious in Buddhism. This may be related to there being 13 sects in Chinese Mahayana. The number 13 is also reflected in Buddhist architecture as evidenced by the 13-story Famen Pagoda as well as the 13-floor Potala Palace (布达拉宫) in Tibet.
These coins are the first turtle shell coins discovered in China and may also be the earliest coins made of turtle shell ever found in the world. The inscription on the coins date them to the Tang dynasty. Because there is no mention of turtle shell coins in Tang dynasty historical texts, little else is known of their origin.
It should be noted that during the Han dynasty (汉朝) the Chinese did make coins in the shape of a turtle shell but these coins were made of silver and not turtle shell.
In Buddhism, a pagoda is a burial chamber which stores a sarira (舍利子) which is a “relic” of the body remaining after cremation.
Although the turtle shell coins were a significant find, the major discovery in the underground vault was the relic of the middle finger bone of the Buddha’s left hand. This did not come as a complete surprise, however, because historical documents clearly recorded that this “true relic” (灵骨) was kept at the Famen Temple.
This sarira is the only finger bone of the Buddha known to exist.
Many of the other treasures in the underground palace date to 874 AD which was when the chamber door was last closed. The underground palace remained hidden to the world for another 1,113 years.
The underground palace contains a total of 2,499 treasures from the Tang dynasty including gems, jewelry, art pieces, gold and silver utensils, and numerous silk fabrics woven with gold thread. There is an embroidered dress of Wu Zetian (武則天) who reigned during the years 690-705 AD of the Tang dynasty and who was the only official female monarch in Chinese history.
Also found was a 1.96 meter long “stick” made of gold and silver. This “stick”, and a number of the finest celadon ceramics, are believed to have been gifts from Emperor Yizong (唐懿宗) who reigned during the years 859-873 AD of the Tang dynasty.
The underground treasures, including the turtle shell coins, are now on display at the fully remodeled “Famen Temple Cultural Scenic Area” (法门寺文化景区).