The red copper you see is the base material and the gold colour looks to me fire burned gold like in a lot done on the earlier days . I think that the copper has been treated with a acid to get the design and after that the gilding .
The vase inside the gilded copper is a normal ceramic small vase so must have been a long job to get it surrounded with the copper before etching and the gilding . But maybe there's some better explanation about the way it's made ?