Wilton Diptych International Gothic style, and the nationality of the unknown artist is probably French or English. The Wilton Diptych is painted on two panels of Baltic oak, set in frames of the same material and joined by two hinges so that it may be closed to protect the inner painting. The inner faces of the panels are in excellent condition for their age, though some glazes have been lost, but the outer faces have paint losses from handling. The painting is in tempera, the ground paint being mixed with egg yolk and laid in thin glazes. The background and many details
Saint Peter Martyr Altarpiece testimony) also mention a second altarpiece by the artist in the same church, also dating to 1476, now known as the "Saint Peter Martyr Altarpiece"'. It is therefore theorised that the altarpieces were both dismantled during rebuilding of the church in 1776, then sold to the antiquarian Grossi who sold all the panels separately and grouped some of them into the altarpiece that Cardinal Zelada bought from him. Federico Zeri and Rodolfo Pallucchini then joined the altarpieces together, initially referring to the first (the high altarpiece), the "Pietà" in the Metropolitan Museum, and then to the "Madonna" in the Museum