One man’s insulation is another man’s treasure.

An Illinois couple’s home renovation led to the discovery of oddball antiques hidden in the walls, including a still-working, circa-1904 lightbulb, according to Jam Press.

Emily and Ash Smith moved into the 134-year-old house in Belleville with their two kids in September 2017 and immediately began restoring the Victorian built in 1887.

The home’s first owner — Peter Martin Romeiser — apparently bought the lightbulb at the 1904 St. Louis World’s Fair, Emily, 34, said. The couple searched the Belleville Historical Society and Ancestry.com to learn more about the home, according to a feature in St. Louis Magazine.

Romeiser was an “incredibly progressive” business owner, she said, and the purchase came just 14 years after Thomas Edison began manufacturing the lightbulb.

Her husband, a 36-year-old Air Force major, tested the bulb’s conductivity with a multimeter and was shocked to find a “low frequency.”

“I’m too nervous to try it because our lamps are so much stronger today,” she said.

The renovation also uncovered an old shopper card under a floorboard, dominoes, a children’s game, a tool grinder and a glass soda bottle with its original cork.

They also found was an early 20th-century baby shoe inside a crawl space. Emily posted a number of the treasures on Instagram.

“Each and every time we’ve uncovered something new, it excites us to try and come up with how that item got there in the first place,” Emily said. “It’s almost like putting yourself into that moment in 1887 or 1904 or the 1950s. I also start to daydream about what else there is left to find. What else is still hiding from us?”