Assets like this are one of the complexities in calculating national import and export figures.

For example, imagine there's some German-owned gold in a UK bank vault, the owners sell it to a UK broker who sells it to a Chinese investor? The physical bars don't move, but on paper it's been imported to the UK then exported.

But a lot of people looking at export figures are expecting to learn things about the manufacturing industry, and picturing exports as washing machines, cars and computer chips - which imply lots of well paid jobs for skilled labour. So the UK reports import/export figures with 'non-monetary gold' listed separately.

(The fact flows of gold are highly volatile allows a classic bit of political sleight-of-hand - if you include gold, UK exports are both up and down since Brexit, depending on the pair of dates you choose)