Crucifixion Diptych (van der Weyden) that they could be the left and center panels of a triptych, that they formed either the wings or shutters of an altarpiece, or that they were intended to decorate an organ case. The train of the Virgin's robe continues onto the right panel, which evidences that the panels were intended to lay side-by-side rather than separated (as the wings of an altarpiece would have been). Art historian E. P. Richardson proposed that they were the center panel of the lost Cambrai altarpiece (executed between 1455 and 1459), a single painting now split into two parts. Art historian Penny Howell
Early Netherlandish painting time. That hinged works could be opened and closed served a practical purpose; on religious holidays the more prosaic and everyday outer panels were replaced by the lush interior panels. The "Ghent Altarpiece", completed in 1432, had different configurations for weekdays, Sundays and church holidays. The first generation of Netherlandish masters borrowed many customs from 13th- and 14th-century Italian altarpieces. The conventions for Italian triptychs before 1400 were quite rigid. In central panels the mid-ground was populated by members of the Holy Family; early works, especially from the Sienese or Florentine traditions, were overwhelmingly characterised by images of the enthroned