“Repoussé or repoussage refer to a metalworking technique in which a malleable metal is shaped by hammering from the reverse side to create a design in low relief. Chasing, chased work, or embossing refer to a similar technique, in which the piece is hammered on the front side, sinking the metal. The two techniques are often used in conjunction.
Many metals can be used for chasing and repoussé work, including gold, silver, copper, and alloys such as steel, bronze, and pewter.
These techniques are very ancient and have been extensively used all over the world, as they require only the simplest tools and materials, and yet allow great diversity of expression. They are also relatively economical, since there is no loss or waste of metal, which mostly retains its original size and thickness. Toolmarks are often intentionally left visible in the result.” - Source Wikipedia/Repoussé