I've worked with commodity exchange software, for cocoa. It is amazing the amount of rules they have come up with. Not only you have grades, but there's a whole

I've worked with commodity exchange software, for cocoa. It is amazing the amount of rules they have come up with. Not only you have grades, but there's a whole process to store, maintain, audit, split and combine commodities. What's more, once it is accepted at a warehouse, everything else happens electronically, until such a time the commodity actually has to be moved somewhere. In the mean time, all that gets traded is the paper. Or its electronic version, or paper. If paper is involved (usually is), then there are business specializing in storing it, and providing certification that you indeed own this piece of paper, with in turn says you own X tonnes of cocoa of such grade at some location.