Retablos are small paintings of religious subjects. Most were painted on tin, dating from the 19th Century, but rare ones as much as 300 years old exist; the old ones usually painted on copper or wood. Subjects can be divided into three categories: 1) Jesus Christ, 2) The Virgin in her various manifestations, and 3) a wide variety of saints, angels, and other holy figures. On the left, a retablo bears a rendering of the patron saint of my town, St. Michael.

Their style owes much to 17th-century Spain. Concerned by the rapid spread of New World settlements that were springing up faster than churches could be built, the Spanish Catholic Church sent painters overseas to teach indigenous artists how to make paintings for use in home chapels. Since then, countless thousands of them have been created.

The term retablo means "behind the altar," after the location where they were displayed.

Although retablos have roots in classical Spanish painting, they clearly are Mexican folk art: charming, colorful, and eminently collectable. Demand has increased rapidly in recent years, and therein lies an opportunity for my friend and noted international merchant, Clint. Here he is in an antique store in Zacatecas, checking out a selection of retablos in an effort to build his stock.

Visitors can't just wander about the countryside visiting ruined haciendas and making offers for antiques anymore. Mexican dealers are experiencing booming demand, and they scour the country for pieces that have survived. The likes of us don't have a chance. Clint looks for retablos in retail antique shops, but for him there still are substantial margins, because he resells them to collectors in the states. They are willing to pay much higher prices than retablos can command in Mexico.

Clint has a unique style of networking. Stopping two mariachis on the street, he asked them something like, "Hey. Know where I can buy some retablos?" I dunno—I probably wouldn't have tried that approach. But for him it worked. They steered him to this imposing building.

A former mercado where meat and vegetables were sold, it has now been converted into an elegant shopping mall.

The high, paneled ceiling, the cast-iron columns, the tiled floors have all been retained and restored. Individual stores have been constructed as free-standing glass enclosures. For my money, the architect gets an A for this building. It's so fine that it looked a little rich for our blood.

But most antique shops have a way of being cluttered, eclectic places with flexible pricing, and the one in the mercado was no exception. Clint hit pay dirt here: three fine retablos at good prices.

Back in San Miguel, Clint shows off one of his trophies: a charming Madonna and Child in an ornate frame. It's easy to see why demand for these objects is so high.

I wonder if Clint will actually manage to part with this one. He has several nice ones hanging in his home, and I suspect he loves them primarily for their appeal, and not so much for their potential profits.