Rob Kirby published an article spotting a huge anomaly on the Gold and Silver positions held by the US banks. From July to August, short positions in Silver increased by 500%, rising from 6,200 to almost 34,000 contracts and Gold short positions increased about 1,100%, rising from about 7,800 to more than 86,000.
The notional for Gold contracts is 100 ounces while the notional for Silver contracts is 1000 ounces. So basically, these US banks are short about 34,000,000 ounces of silver and about 8,600,000 ounces of Gold.
Here are the relevant CFTC links: July, August
Same applies for non U.S. banks.