Vaultoro's vault operator, Brinks Switzerland, sends a confirmation of Vaultoro's gold holdings whenever about once a week. This document is published on the audit page.
Vaultoro hereby declares and guarantees that it functions at 100% full reserves. This means that Vaultoro will never use as collateral, lend out, hypothecate, create a derivative transaction of any type, with any Bitcoin or gold held in bailment for its clients. All gold will remain the property of the user through a Vaultoro bailment until sold by or physically withdrawn by its owner.
Read more about the levels of transparency Vaultoro goes to while keeping users private.