Doesn’t that just mean that they’ve been manufactured by Mitsubishi Materials Corporation?

And I imagine they could trivially track them, like most modern gold bars sold/collected in this volume.

	▲	yreg an hour ago \| parent [-]
		There is no mystery, the donor just donated the money anonymously. All that means is that the city won't publish the name of the donor. It doesn't mean "no one knows who has paid for this".