I thank Jeff from http://www.treasurelore.com for this interesting item. It is an article from a NY Times on July 2, 1882 about how gold was packed in kegs and transferred between the US Banks and Europe aboard ships.
Quite surprising is the fact that some banks shipped their gold without insurance, dividing up the cargo between 4 or 5 different carriers.
Also interesting is that they tried to use large denomination double eagles, as the abrasion from the rough ocean crossing would cause a loss of up to 20 ounces of gold in a "$1,000,000 shipment", which would have weighed 62,500 ounces. This would equal about $320 in the value of the day. ($17,000 in today's value).
The Ancona, one of the three shipwreck arrests filed by Odyssey Marine, sank 33 years after this article first appeared. Perhaps it is still pertinent to the supposed on board gold shipment, thought to be worth at least $20M in today's dollars.