<P> Cracking along the vertical join of the wooden panels was severe enough to warrant a third restoration in 1982 . Raking light revealed that modern varnishes had yellowed, while further overpainting was found . Working under ultraviolet light, paint from earlier restorations was removed, uncovering lost colours and landscape details, including the snow - capped mountains and birds of prey on the upper left . Restorers found clues to sources of confusion in earlier restorations, especially the unusual positioning of Francis's tonsure and Leo's feet, which were discovered to be crossed under his body . </P> <P> Research in the late 19th century lead to what Rishel describes as "one of the thorniest conundrums in the study of Early Netherlandish art", as efforts were made to establish authorship and date the panels in terms of precedence . The panels are neither signed nor dated, and have proved especially difficult to attribute . Establishing an approximate date of completion is usually one of the most important factor in attributing an old master painting . Dendrochronological analysis of the Philadelphia panel dated its growth rings to between 1225 and 1307 . It was established that the board was cut from the same tree as the wood of two known panels by van Eyck, the Portrait of Baudouin de Lannoy (c. 1435) and Portrait of Giovanni di Nicolao Arnolfini (1438). These have tree - rings that developed between 1205 and 1383, and 1206 and 1382, respectively . Examination of the sapwood suggests a felling date of around 1392 . Assuming a typical 10 years of seasoning before use, any of the paintings could have begun from around 1408 onwards . The Turin version is painted on two glued boards, vertical to the image . The rings from board I are dated between 1273 and 1359, those of board II from 1282 to 1365 . </P> <P> Based on the perceived "faulty proportions" of the figures, Ludwig von Baldass suggested a date early in van Eyck's career, around 1425 . He attributes the unusual positioning and anatomy to a young and relatively inexperienced painter, one who was still experimenting . He notes how the landscape and individual elements are similar to Hubert van Eyck's style, but that the close observation of nature reveals Jan's hand . Luber suggests a slightly later date of about 1430, during the period van Eyck finished the Ghent Altarpiece . She bases her supposition on the fact that van Eyck's employer Philip the Bold sent him to Portugal in the late 1420s; he would have been unavailable for a commission until his return in 1430 . Furthermore, the landscape details, which correlate to van Eyck's work of the period, combined with the return from pilgrimage late in the 1420s of the Adornes brothers (who may have commissioned the two paintings), suggest a completion date of about 1430 . </P> <P> A free copy from some two generations later is in the Prado in Madrid . This is in a vertical format and measures 47 x 36 cm . A large tree is added at the left, and the foreground rocks extended higher . The landscape is somewhat different, and reflects the world landscape style of Joachim Patinir, to whom the painting has been attributed in the past . This was largely because the jagged peaks in the distance have been added to and altered to Patinir's trademark depiction of the distinctive landscape of Dinant, his hometown . This panel was attributed by Max Jakob Friedländer to a "Master of Hoogstraten", an anonymous follower of Quentin Massys, and dated around 1510 . The awkwardness of the figures has been rectified, the placement of his feet and knees "made more rational" according to Rishel, but St Francis stares at the apparition . Another copy, placed tentatively in Brussels c. 1500, is probably a copy of the Turin version . </P>

Jan van eyck st francis receiving the stigmata