(CNN) Hundreds of World War II dog tags disappeared for years as Antonin DeHays constantly visited the National Archives.

On Monday, the 33-year-old historian was sentenced in federal court to 364 days in prison for stealing the artifacts. He sold most of them on eBay and elsewhere, the Department of Justice said.

Since 2012, DeHays had been sneaking out of the College Park, Maryland, facility with the artifacts. He took at least 291 dog tags of American soldiers whose planes were downed in Europe during WWII. He also took 134 other items, which included identification cards, a bible, and pieces of downed US aircraft, the DOJ said.

Certain dog tags were "burnt and show some stains of fuel, blood . . . very powerful items that witness the violence of the crash," he told a potential buyer in a text message.

DeHays also described a dog tag as "salty" as he tried to explain its war-related damage and mentioned a "partially burned" American Red Cross identification card when he texted another potential buyer.

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