Memo for the amateur. The sellers of works of art or collection, the antique dealers or the companies(societies) of sales, have the obligation(bond) to free(deliver) to the buyer who asks for it an invoice, a receipt, a sale contract or an extract of the report(fine) of the public sale. Further to the various disputes which were able to exist on the authenticity of works of art during transactions (deals) – and to avoid a fuzziness(vagueness) harmful to the buyers-, the decree of March 3rd, 1981 exactly defined the mentions(grades) of certificates of authenticity or descriptions of the catalog of auction. This arrangement ( measure) so creates a real valuable scale(ladder) of furniture or oeuvres of art. When the certificate mentions the term “time”(“period”), followed by century or of historic period, it means that the piece of furniture is good of indicated time (period). Also, the name of an object followed by the reference to a historic period, a century or a time (period), guarantees to the buyer that this object was produced during reference period (example: ” Armchair Directory “). On the other hand, if one or several parts(parties) of the object are not of mentioned time(period), the buyer must be informed about it. If the certificate indicates that a piece of furniture carries(wears) the stamp of a particular cabinet maker, it pulls(entails) the guarantee that the latter is there actually the author, unless the authenticity of the stamp is doubtful. In case the document indicates that the good(property) is “in the style of”, the buyer has no particular guarantee relative to the date. This mention(distinction) means simply a realization in the style or the taste of time(period) indicated (” secretary of style Worsens “). The writing(editorial staff) of certificates of authenticity or invoices for works of art contains some more of subtlety; it is thus advisable to be attentive to it during any acquisition. If the invoice mentions ” work of “, “by”, ” signed of “, or presents a description of the work with the name of the artist without limitation or reserve on the authenticity, it guarantees that the work was well completely realized by the indicated artist. It is thus about an authentic work. As soon as there is a doubt, even small, on the paternity, the certificate will have to indicate ” attributed(awarded) in “. This mention (distinction) followed by the name of the artist guarantees that the work was realized during the period of production of the concerned artist, and that there are serious assumptions so that the work is most probably of this artist. In this hypothesis, the authenticity of the work can be refuted or established later by new elements. When the document of sale describes the good(property) ” as workshop(studio) of “, it means that the work was executed in the workshop(studio) of quoted master(teacher) or under its direction(management). This mention (distinction) must be necessarily followed by an indication of time (period), in the case of a family workshop(studio) having kept(preserved) the same name on several generations. If the work of art is described in reference to a “school”, the author of the work is a pupil of quoted master (teacher). The work must have been realized of alive of master (teacher) or for the deadline(extension) inferior fifty years after its death. If it is the place which is specified, the employment(use) of the term ” school of ” guarantees that the work was executed during the duration of the existence of the indicated(appointed) artistic movement, the time(period) of which must be specified, and by an artist having participated in this movement (example: ” the school of Pont-Aven “). Finally, expressions as “in the style of”, ” in the taste of “, “in the style of”, ” kind(genre) of “, “according to”, “like”, confer no guarantee on the authenticity of the work as regards time(period), the identity of the artist or the school. It is thus necessary to be very watchful in formulae drafted in any document bound(connected) to a sale of works of art or collection. Indeed, their consequences, artistic, legal and financial, are essential. Since the decree of March 3rd, 1981, these formulae allow to establish, in the closer, the real ID card of the work.