All in all, it was hiding behind just another brick in the wall.

A collection of rare gold coins nearly lost to history after its owner passed away has fetched nearly $4 million at auction.

The impressive coin collection was gathered over a lifetime by Paul Narce, a numismatist residing in Castillonnès, France, who passed away last year at the age of 89, according to the Times of London.

Prior to the auction, coin specialist Thierry Parsy remarked, “This is the first time I’ve witnessed such a significant collection being auctioned, both in terms of its volume and the caliber of the pieces.” The auction took place at the Beaussant Lefèvre auction house in Paris, as reported by CNN.

“Narce, who lived a modest life and didn’t see a lot of the world, spent all of his money on his collection,” said Parsy.

His rare prizes were meticulously labeled — the collection reportedly numbered more than a thousand pieces, some dating back centuries.

The collection included items from the Kingdom of Macedonia, originating from the period 336-323 BC, along with almost complete sets of coins from the eras of French Kings Louis XIV, Louis XV, and Louis XVI. Notably, there were coins from just before Louis XVI’s execution by guillotine in 1793.

Parsy said that Narce clearly “knew what he was buying,” which seemed unusual given that he was an unknown.

In fact, the coin expert said that the treasure trove “could have remained undiscovered forever” — had the notary in charge of the deceased’s estate not heard of Narce’s unique hobby from local villagers.

The elderly collector had no children or heirs and had moved to a nursing home after his sister Claudette, with whom he collected the coins, passed away a year prior.

Along with the aforementioned collection, they found “masterpieces of gothic art” and ten cloth pouches, each containing 172 “Napoléons” (golden 20 franc coins) — amounting to an ingot of gold.

After an extensive search of the property, the notary finally located the treasure chest — hidden behind the picture on the wall of a storage room.

The coin collection went under the gavel for an eye-popping $3.8 million, far exceeding the pre-auction estimate of around $2.3 million.

Meanwhile, the francs, valued at around $115,650, will be auctioned off separately.

The money will reportedly go to distant cousins of Narce.

Pierre Sicaud, mayor of Castillonnès, couldn’t believe that the senior and his sister had amassed such an incredible collection under the radar.

“They were very polite, very modest people who lived in an ordinary house,” he explained.