Written by Kate Springer, CNN

It's not every day you get to hold a 700-year-old banknote in your hands. And for Ray Tregaskis, head of Asian art at Australia-based Mossgreen auction house, the rare opportunity felt like the discovery of a lifetime.

Tregaskis came across the treasure while inspecting the underside of a 14th-century wooden Buddhist sculpture. There, hidden inside the cranial cavity, he found a crumpled-up piece of paper.

Upon closer inspection, the unassuming parchment turned out to be a 700-year-old Ming Dynasty banknote -- among the earliest printed currency in China.

"This is the first time, that we know of, that a banknote has been discovered inside a wooden Buddhist sculpture," says Tregaskis. "We were surprised, astonished, and once we had translated (the text), very excited!"

On Sunday, the banknote and Buddhist sculpture went up for sale as part of the Raphy Star Collection of Important Asian Art auction in Sydney, Australia. Together they sold for $48,032 AUD ($35,806 USD).

Full of surprises

Antique Buddhist sculptures are well-known treasure troves, but this banknote proved to be a unique discovery.

"It's typical to find materials such as mantra rolls, relics, grains, incense and semi-precious stones that have been placed inside gilt bronze sculptures by a monk or lama," says Luke Guan, a Mossgreen Asian art specialist.

"But we've never heard of anyone finding money inside a wooden sculpture before."

It's impossible to know for sure how the money ended up hidden inside the artwork, but thanks to dates printed on the note, Mossgreen's specialists have been able to verify the age of the sculpture and better understand its history.

Most likely, they believe a patron may have placed the banknote inside while commissioning repairs -- an estimated 40 or 50 years after the sculpture was first made.

This date itself is estimated to be sometime in the 14th century, as both the bank note and carving style suggest the artwork was created during China's Hongwu period.

courtesy mossgreen auctions

The wood sculpture represents the head of a Luohan, a wise person who has passed through the four stages of Enlightenment and reached Nirvana, in Buddhist culture.

Appearing calm and confident, the sculpture's expressive features are clearly visible in the exaggerated lines and curves of the face.

According to Guan, the sculpture would have been part of a series of anywhere from 16 to 500 sculptures, usually kept inside a Buddhist temple for worship.

Sign of the time

The banknote itself is more than 700 years old, and was made during China's Ming Dynasty, which spanned almost 300 years, from 1368 to 1644.

The period under the Hongwu Emporer, Zhu Yuan Zhang -- the founder and first emperor of the Ming dynasty -- was a prosperous era fueled by strong international trade and a growing population.

During this time, China replaced its traditional currency of silver and gold with paper money.

The bill is endorsed by the emperor himself, with three official red seals and a line that reads: "Authorized by the Department of Finance, this bank note has the same function of coins. Those who use counterfeit banknotes will be beheaded, the whistle-blower will be rewarded 250 Liang silvers plus all the properties of the criminal. The third year of Hong Wu period."

The "one guan" banknote was the highest denomination available at the time, and was equivalent to "one liang" of silver -- which is a face value of about 660 RMB or roughly $98. If sold alone, its auction value today is estimated to be between $2,000 and $4,000.

Aside from its inherent value, the banknote lends additional insight into the era.

At the time, bills in China were crafted from handmade mulberry bark paper and printed using a carved woodblock, a technology that has played an important role throughout Chinese history.

Dating back to 868 AD, this printing method enabled the dissemination of information, art and literature.