Looking at the June 2020 Perth Mint Balance sheet which predated the SilverSqueeze and the sale of the gold ETF.
As i understand it, if you deposited $1000 in allocated or unallocated metal, that would show up on the balance sheet as a $1000 asset in inventory, and as a liability of $1000 of "precious metal borrowings".
Looking at the liabilities on the balance sheet below ... According to their notes, it sounds like the "interest bearing borrowing" of $1.721 billion is probably leased gold. And the "precious metal borrowings" are the silver and gold in Depository Accounts (including unallocated) of $4.676 billion. Those two total $6.398 billion.
OK fine. Under Assets, the inventory is $5.997 billion. So where's the missing $401 million of metal?
Balance sheet source:
https://www.perthmint.com/documents/Annual%20Reports/The%20Perth%20Mint%20Annual%20Report%20FY19-20.pdf
(20min delay)