William Smith was ahead of his time. In the 1790s, Smith, an English surveyor and amateur fossil hunter with little formal education, was hired to survey possible canal routes across the country, a job that required a deep understanding of the rocks where digging might be necessary. In his work, he observed that different layers of rock held distinctive fossils in a pattern consistent across England and Wales. “Each stratum,” he wrote, “contained organized fossils peculiar to itself.”

“He noticed that the rocks he was excavating were arranged in layers,” author Simon Winchester would later write. “More important, he could see quite clearly that the fossils found in one layer were very different from those found in another. And out of that realization came an epiphany: that by following the fossils, one could trace layers of rocks as they dipped and rose and fell — clear across England and, indeed, clear across the world.”

The result would be “the map that changed the world,” as Winchester wrote in his best-selling 2001 book of the same name.

“It is a map that heralded the beginnings of a whole new science,” he wrote. “It is a document that laid the groundwork for the making of great fortunes — in oil, in iron, in coal, and in other countries in diamonds, tin, platinum, and silver — that were won by explorers who used such maps. It is a map that laid the foundations of a field of study that culminated in the work of Charles Darwin.”

Around 200 years later, a rare first edition copy of his seminal work was unearthed. It’s thought to be only one of 70 in existence, and it could possibly be worth six figures. The newly discovered copy of the map was digitized and put on display for the first time to celebrate its bicentennial this week.

According to the Geological Society of London, there were geological maps that came before Smith’s, but they only identified rocks by type. Smith’s map attempted to classify rock by age and deposition, essentially showing people what is under their feet. John Henry, chairman of the history of geology group at the Geological Society, explained to LiveScience:

He was the very first to realize that fossils had particular detailed characteristics that he could then tie to certain geological strata. … [Before Smith] people just thought fossils were decorations and ornaments … Nobody thought they were a key to making a sensible order of the geological structure, or using them to predict where economic materials were.

“It’s very exciting — you don’t find things like this very often,” Henry told Live Science. The rare map was tucked inside a leather sleeve case not seen for 40 or 50 years. Archive assistant Victoria Woodcock found the map last year.

“The map was found among completely unrelated material, so at first I didn’t realise the significance of what I’d uncovered,” she said in a press release. “I was astonished. It’s the kind of thing that anyone working in archives dreams of.”

The hand-colored map is thought to be one of the first 10 produced by Smith, who only made approximately 370 copies.”These maps are extremely rare,” Henry said in a press release. “Each one is a treasure, and to have one of the very first produced is tremendously exciting.”

In Smith’s time, the Geological Society was reluctant to accept his vision and disliked his working-class background. The map, published in 1815, didn’t gain acclaim for 10 years. During that time Smith had money problems, but found work with large landowners, surveying their land for water usage and for coal.

Eventually, the Geological Society changed its mind about Smith and the value of his work. Although he was never a member, in 1831 the society awarded Smith its highest honor, the Wollaston Medal, and named him the “Father of English Geology.”

On Monday, in honor of Smith, Sir David Attenborough unveiled a plaque at his former residence in London.