Most of bullion dealers don't store their customers' bars and coins themselves, but use partner companies specializing in the secure storage and warehousing of precious metals.
These are international companies, so they give investors the choice between very safe jurisdictions such as Switzerland, Toronto, New York or Singapore.
Safekeeping gold in professional storage units guarantees its traceability and facilitates its resale. Indeed, having never left the professional circuit, the origin of the precious metals is guaranteed.
Here is a more detailed explanation of the differences between direct ownership and mutual ownership.