This is an excellent short video proposing a ratio between disclosed and undisclosed gold holdings.
http://www.ottawabullion.com/belangp-so-where-is-the-gold/
If I understand his data correctly, it represents mining output from 19th Century forward. If this is correct, there is all that pre-19th Century gold to consider as well. The idea that all the gold ever produced will fit into a [name of container here] is absurd.
p.s. Narrator Belangp follows Another and is conversant with FOFOA.