All this information undoubtedly indicates that a member of Leonardo’s studio produced the Prado panel and that the copy and original were produced at the same time and in parallel (see fig.20). With regard to who the artist might be, the pictorial handling is not comparable to the style of pupils or collaborators such as Boltraffio, Marco d’Oggiono or Ambrogio di Predis, who have a defined artistic personality. However, it is possible to locate this work stylistically in a Milanese context, close to Salaï or perhaps to Francesco Melzi, Leonardo’s most trusted pupils, heirs of his work and the painters who had direct access to his landscape drawings.
The high quality of the materials used for the Madrid panel suggest that it was an important commission. In addition, up to now all known copies of La Gioconda were executed after its creation and reproduce what was a celebrated work from an early date. Technical analyses demonstrate that the Prado’s version was executed at the same time as the original, supporting the hypothesis of a workshop “duplicate” produced at the same time and with direct access to the gradual process of creation of Leonardo’s original work.