Since 1956, Die Proofs have been made and their production has been strictly controlled by the government stamp printery. The quantity produced is limited to about twenty copies. They are made by hand press from the unhardened Die on a piece of thick, high-quality paper. Each Die Proof bears a embossed administrative control seal which makes reproduction virtually impossible. Before 1956, Die Proofs usually were produced by the artist himself. They are, therefore, also known as "Artist Proofs." Less control was exercised, and, although most Artist Proofs are quite scarce, in some cases larger quantities were made. Die Proofs are made in various solid colors -mostly black- and usually bear the artist's signature in Pencil.