CONCORD — A Greenland man has pleaded guilty in U.S. District Court to mail fraud in an investment scheme that operated from November 2003 to July 2010.

The U.S. Attorney’s office said William Orestis, 64, faces up to 20 years in prison and a $250,000 fine at his scheduled sentencing on Sept. 27.

Orestis and another person conspired to solicit money on behalf of a fraudulent investment company, Equivest, LLC, and falsely assured investors that their money would purchase foreign currencies and support Equivest’s business activities.

Orestis and his partner provided investors with false account statements, claiming impressive profits earned by other investors in Equivest accounts.

Orestis and his partnter assured some investors that their accounts would earn a minimum of 12 percent annually, with promises of interest rates as high as 18 percent.

Orestis and his co-conspirator obtained approximately $769,200, but used only a portion of it to purchase foreign currencies. They made “interest” payments, totaling approximately $132,200, to some investors. Investors lost a reported total of approximately $637,000. The case was investigated by the United States Postal Service and prosecuted by Assistant United States Attorney Bob Kinsella.