Did some quick googling. Have included 2 links below. One is a Wikipedia link on Bunker Hunt, and the other is a Jan. 2011 article on SLV. The Hunt article says that at one time they owned about 100 million oz's of silver. The SLV article says that back in Jan. they owned about 352 million oz's of silver. Read some articles since that said that SLV had to sell plenty of silver in the drop from about 50 to about 33. However if you look at it its 100 million to 352 million for just one ETF.
Now did Bunker Hunt buy silver under his name or did he have a coorporation (and example would be HuntSilETF) that he bought it under. Either way he took delivery and stuffed it in a vaults much like ETFs.
http://en.wikipedia.org/wiki/Nelson_Bunker_Hunt
http://www.zealllc.com/2011/slvetf2.htm