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 gilded stash had been amassed over a lifetime by numismatist Paul Narce, who lived in Castillonnès, France, until his death last year at 89, the Times of London reported.

“I have never seen such a major collection go on sale from the point of view of quantity and quality,” coin expert Thierry Parsy said in a statement ahead of the sale, which went down at the Beaussant Lefèvre auction house in Paris, CNN reported.

“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.

These included pieces from the Kingdom of Macedonia, dating to 336-323 BC, and nearly complete sets of coins exchanged during the reigns of French Kings Louis XIV, Louis XV and Louis XVI — including some minted just before the latter’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.