There’s something to be said for yard sales.

A small, unframed black ink sketch of a mother and child, bought for $30 at a house clearance in Concord, Mass., turned out to be drawn by early-Renaissance artist Albrecht Dürer some 500 years ago worth $50 million.

Hidden in plain sight

The astonishing thing is that finds like this at rummage sales, flea markets, as well as the attic, basements, and within walls, are not unusual. (More about that in a moment). The Dürer discovery went something like this.

The drawing belonged to a former architect, Jean-Paul Carlhain.

His children who sold the work for $30 thought it was a reprint. The buyer, an unnamed Massachusetts man, didn’t know what he had, either.

Then, two years later, an art dealer, Clifford Schorer, learned of the work and asked to see it. And as he told The Art Newspaper, "It was an incredible moment” when he saw it was Dürer’s work.

Proof positive

To ensure that it wasn’t a forgery, the drawing was put through an authentication process for two years proving it genuine, though it was a previously unknown Dürer.

One big clue: experts recognized Dürer’s monogram – “AD” – which was written with the same ink used in the sketch. Also, the paper for the sketch bore the same watermarked – a trident – that the artist used in more than 200 works attributed to him.

The sketch, newly named "The Virgin and Child with a Flower on a Grassy Bench" and dated 1503, is now thought to be a preliminary outline for Dürer’s painting "The Virgin Among a Multitude of Animals".

The drawing is currently on view at the Agnew’s Gallery in London. The Massachusetts buyer has already been advanced $100,000, and when the work is sold, will receive the remaining amount due him.

As for fine art discovered in unlikely places, just this past May, this column noted another discovery, this time in an attic – a portrait by Giovanni Batiste Tiepolo, "Portrait of a Lady as Flora," that sold for $3.1 million.

And you may remember that in 2015, a small, early painting by Rembrandt was found in a basement in New Jersey.

Covered in dirt and yellow varnish, it was unrecognizable. When cleaned, experts knew who did it.

The experts, Nye and Company auctioneers, told Reuters that the unearthed Rembrandt was “remarkably unremarkable” and they didn’t expect much. But the bidding reached $870,000, far beyond the estimate of $500. But that wasn’t the final sum.

The name of the art game is a famous name

This “unremarkable” painting went for $3 million. Clearly, the famous name served. Rembrandt is again in the news this week when the Netherlands announced paying $198 million for one of his self-portraits.

Titled "The Standard-bearer," this portrait was in the collection of the Rothschild family in France for the last 177 years.

The Netherlands, Rembrandt’s native land, wants to bring his work home.

All of which tells the tale; unexpected places like attics, basements, and flea markets are tantamount to lost and found departments for art treasures.