Focus on San Gregorio Polyptych and analyze the History.
The polyptych is signed in the cartouche visible on the step in the central panel. It was commissioned for the convent annexed to the church of   Santa Maria extra moenia in Messina, also called  San Gregorio, whence its modern name. The panels were originally connected by a carved frame  in Neo-Gothic style, which was likely removed from as early as the 16th century. The work is in poor state. One of the panel was removed in the 16th century or later, and in 1842 there was a drastic restoration of what remained. In 1908, the former convent where the work was destroyed by the 1908 Messina earthquake, leaving its art pieces exposed to the rain which fell in the following days. In that occasion, large parts of the Madonna's mantle and of St. Gregory went lost.
Recovery interventions began in 1912, under the direction of Luigi Cavenaghi. This regarded, in particular, the side panels, including a restoration of lost parts basing on existing photographs (such as one of St. Gregory's hands). A new restoration was performed during 1940–1942 by the  Istituto Centrale del Restauro of Rome, followed by another (Angel of Annunciation panel) in 1981. In 2005–2006 there was a complete check of the polyptych, when it was exhibited at the Quirinal Palace. Some details, which had been covered by later repaintings and restorations, were recovered: they include the original decoration with vegetable motifs of Mary's mantle (originally completed by a gilt decoration, now lost).
Quirinal Palace 1908 Messina earthquake polyptych