Sorry, we provide the burners clean but not stunning like this one
A commercial polishing job will cost over $100, but you can do it yourself. My thanks to Dave Johnston of Speights Brewery in Dunedin who's looked after the huge antique shining copper beer vats there for decades.
On his advice, mix a 150gm (5 oz.) packet of tartaric acid ($1.85 or so in a supermarket) into 600 millilitres (1 pint) of hot water. Rub it lightly onto the copper and brass of the burner with a fine grade Scotch-Brite cloth or towel (not too coarse a cloth or it will scratch the surfaces). Leave for a few minutes, then rub hard using more of the liquid.
Clean it all off with clean hot or boiling water, and dry with a clean cloth or towel to avoid smears. You can use gloves with the mild tartaric acid but Dave doesn't bother.
The brass door will still go a bit brown with the heat when the burner is used for the first time. Painting a clear lacquer on after that will ensure it shines longer.