Police are investigating the attempted sale of a group of rare United States coins, including a gold 1879 $4 coin for $400,000. The seller had sold fake coins before, but this time, several official websites that certify the quality and pricing of expensive coins for collectors and dealers were asked to investigate, including the U.S. Department Office of Inspector General (OIG).The fake coins are now held by Irvine, California, police while they search for the forger. About a dozen real 1879 gold coins are known.The fake coins were in a counterfeit holder that copied a real one by Numismatic Guaranty Corporation. Reports by several other respected coin experts say coins have been forged and collectors should watch out for well-made fakes.