There is not alot of Tungsten gold stored in any volume because any big buyer of gold will reforge the gold they purchase and the asset is confirmed in quality at that time. Its worth their time to do so, in particular instances there is fraud but it obviously damages the reputation of those involved and is not common place.
I would proceed with "caution". reports of 400 oz. “good delivery” bricks of gold found gutted and filled with tungsten within the confines of LBMA approved vaults in Hong Kong went back to time where Satoshi was still active on this forum. Keep in mind those 400 oz bar were mostly traded on professional markets and turn over are alot lower, yet fakes do exist. Also tampering of serial no. on those bars does happen, consider the following:
DA investigating NYMEX executive - Manhattan, New York, district attorney's office, Stuart Smith - Melting Pot - Brief Article – Feb. 2, 2004
A top executive at the New York Mercantile Exchange is being investigated by the Manhattan district attorney. Sources close to the exchange said that Stuart Smith, senior vice president of operations at the exchange, was served with a search warrant by the district attorney's office last week. Details of the investigation have not been disclosed, but a NYMEX spokeswoman said it was unrelated to any of the exchange's markets. She declined to comment further other than to say that charges had not been brought. A spokeswoman for the Manhattan district attorney's office also declined comment.
"The offices of the Senior Vice President of Operations - NYMEX – is exactly where you would go to find the records [serial number and smelter of origin] for EVERY GOLD BAR ever PHYSICALLY settled on the exchange. They are required to keep these records. These precise records would show the lineage of all the physical gold settled on the exchange and hence "prove" that the amount of gold in question could not have possibly come from the U.S. mining operations – because the amounts in question coming from U.S. smelters would undoubtedly be vastly bigger than domestic mine production."
just be warned. The truth is out there.