The Eastern State Penitentiary museum in Philadelphia is home to a meticulously detailed recreation of the jail cell inhabited by legendary gangster Al Capone in 1929 and 1930. Featuring an ornate desk, patterned rugs, arm chair, and wall art, the exhibit is meant to show what Capone's cell looked like during his time behind bars. But as museum curators recently discovered, one minor detail was out of place.

Atlas Obscura reports that on a recent visit, 13-year-old antiques enthusiast Joey Warchal noticed something amiss. Warchal, who is a collector of antique radios and record players, instantly identified the large cabinet radio included in the exhibit as a Philco A-361, released over a decade after Capone served his jail sentence. Philly.com reports that Warchal emailed museum vice president Sean Kelley about the mistake, offering to track down a period-appropriate replacement.

“As an antique collector specializing in radios," he wrote in the email, "the radio displayed is a Philco A-361, made in January 1942.”

Kelley took Warchal up on his offer, giving the seventh grader a budget of $400 for a replacement. Warchal, who spends his weekends antiques collecting, and has extensively studied 20th century radios, quickly tracked down a Philco Model 76 made in 1929. To celebrate the new radio and thank Warchal for his hard work, the museum will throw a cider and cake ceremony on June 7, when Warchal arrives to deliver the radio.

When asked about her son’s amazingly in-depth knowledge of 20th century radios, Warchal’s mom told Philly.com, “Most kids want toys. He wants antiques.”

[h/t Atlas Obscura]