marketpress plugin - where is puchased product details stored

Hi there
I am writing a plugin to allow people to 1. add feedback to purchases and then 2. list feedback on the store owners store. (like ebay feedback)

I have written most of the plugin but need to add a section to list which items have been purchased by the logged in user.

Where are purchase details stored, is it in the users meta or elsewhere? If you could name the array the details are stored in and the keys that would be useful.

Happy to share the plugin when its finished.