Boccalaco is a textile dyeing technique where areas are prevented from absorbing dye by being sandwiched between boards. It is often referred to as clamped dyeing. However, while later clamped dyeing only distinguishes between the dyed and undyed areas, in the case of the Horyuji Temple's boccalaco, one can observe multiple layers of dyed areas.
夾纈とは、板で強く挟むことによって、染料液に漬けても染まらない箇所をもうける染織技法のこと。いわゆる板締め染だが、後世の板締め染が、染料と白（染まらない部分）の二色を染め分けるにすぎないのに対して、正倉院の夾纈には、多色の染め分けを見ることができる。
View the original at Japan Search →Article 1 states the purpose plainly: prevent trade in stolen goods, find them quickly, and speed the recovery of victims. Article 2 then defines a used article to include, in the same breath, art objects held for appreciation. Dealing in them requires a licence.
The cool part. Article 16 requires a dealer to record every transaction: the date, the item and quantity, its distinguishing features, and the address, name, occupation and age of the other party. Article 15 requires that a dealer who suspects an item is stolen report it to a police officer immediately. So the antique trade runs on a register the police may read, and a painting becomes a second-hand article the moment it has been used once.
Verify at e-Gov 法令検索 →Use it Two-colour foil on uncoated stock gets you most of this at production cost.
Description source: museum curator text, translated — not generated