Your bullion are physically stored and managed by Loomis International at high security bonded storage facilities in Singapore, Hong Kong and Zurich.
Related articles:
What is the fee for storage per year?
http://help.stackermarket.com/en/articles/5355737-what-is-the-fee-for-storage-per-year
Can I visit my bullion and withdraw in person?
http://help.stackermarket.com/en/articles/5355747-can-i-visit-my-bullion-and-withdraw-in-person
Are my bullion holdings fully insured?http://help.stackermarket.com/en/articles/5355742-are-my-bullion-holdings-fully-insured
Is there proof my bullion is physically held in a vault?