Authorities have recovered a stolen 18-carat gold bookmark that reportedly was given to Adolf Hitler by his longtime mistress, Eva Braun. Christian Popescu, a Romanian national, was arrested Tuesday outside a Bellevue Starbucks after trying to sell the bookmark to an undercover agent for $100,000, according to papers filed in US District Court. Federal prosecutors said the bookmark was among several items taken in an auction-house heist in Madrid, Spain, six years ago. At the time, some antiquities experts questioned its authenticity. The bookmark is engraved with a portrait of Hitler as well as an imperial eagle and swastika, and its inscription indicates that Braun gave it to Hitler to console him after German forces surrendered at Stalingrad. "My Adolf, don't worry," it reads, adding that the loss was "only an inconvenience that will not break your certainty of victory. My love for you will be eternal, as our Reich will be eternal. Always yours, Eva. 3-2-43." Regardless of its authenticity, federal agents said its theft broke the law. "Artifacts of historical significance are not souvenirs for illegal sale to the highest bidder," Leigh Winchell, special agent in charge of Immigration and Customs Enforcement's office of investigations in Seattle, said in a statement. Popescu made an initial appearance in federal court Wednesday, where he was represented by a public defender who left without speaking to reporters. The operation began when ICE learned a man was trying to sell the bookmark in the Seattle area. An informant contacted Popescu, who confirmed he had the bookmark and provided pictures. Popescu told the informant he wanted $150,000 for it. Spanish authorities estimated the bookmark was valued at between $13,000 and $17,000, according to court documents. Investigators set up a meeting with Popescu at a Starbucks coffee shop in Bellevue, where the Romanian man showed an undercover agent the bookmark, charging papers said. He was arrested in the parking lot as the agent paid him $100,000. Popescu is being held on one count of sale or receipt of stolen goods. A detention hearing was set for Monday. U.S. Attorney Jeff Sullivan said agents are still investigating how the bookmark arrived in Seattle. Five people were detained in Tuesday's operation, but only Popescu was arrested and charged, he said. In 2002, three thieves walked into the Duran Subastas auction house in Madrid during work hours and stole the bookmark along with several pieces of jewelry from a glass showcase.