The use of the words “Workshop of” followed by an artist's name guarantees that the work was executed in the studio of the master cited or under their direction. A workshop’s name must be followed by an indication of the period if it’s a family workshop that has kept the same name for several generations - see article 5 of Decree no. 81-255 of 3 March 1981 on the prevention of fraud in transactions involving works of art and collectors' items.