Earlier quoted context omitted.
London has an old school gold exchange. Pretty much you can buy and sell by moving a part between vaults (at least that's how I understood it to work in the past). Now I expect it to be just a spreadsheet but who knows.
My understanding is that it’s on shelves in a shared vault and you relabel who owns that shelf/slot/bin.
Because instead of treating each item as an individual thing, they were pooling everything with other items of the same type. So if I send in a brick and say it’s an iPhone 17 and you order an iPhone 17, you might get my brick.