Jackson, a Democrat who represented Illinois in Congress for 17 years, admitted in February he spent campaign funds illegally on personal items, including Michael Jackson memorabilia. The dubious guitar also purportedly was signed by Michael Jackson.
Van Halen raised doubts about the signature after the U.S. Marshals Service announced the auction, WLS-TV, Chicago, reported Friday. Jackson paid $4,000 for the guitar.
"Concerns were raised on the authenticity of the signature of Eddie Van Halen so we need to drill down on that," said Jason Wojdylo, a spokesman for the service.
The auction may be rescheduled once the items in the collection have been reviewed for authenticity, Wojdylo said.
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