Saint James the Greater with Donors in Prayer (front). Saint Sebastian (reverse)

This double-sided panel — Saint James the Greater with donors on the front and Saint Sebastian on the reverse — exemplifies the Flemish altarpiece wing format in which the patron saint of the donor and an independent devotional image occupied opposite faces of the same painted surface. Now at the Museo del Prado in Madrid, the panel arrived in Spain through the long Habsburg commercial and dynastic connection between the Low Countries and Iberia, and the Prado holds one of the world's most important collections of Flemish painting as a direct result of that connection. Pieter Coecke van Aelst painted this work in 1532; Saint James the Greater — the apostle whose cult at Santiago de Compostela drew pilgrims from across Europe — was a particularly apt patron saint for Spanish donors. Saint Sebastian on the reverse, the Roman soldier martyred by arrows who became a protector against plague, was among the most widely venerated saints of the period. The double-sided format doubled devotional content within a single panel's physical footprint.

Double-sided panel painting required careful management of the oak support's structural behavior: as wood responds to humidity by expanding and contracting, paint applied to both sides experiences different stresses, making delamination a particular conservation risk. The Prado's conservation expertise would have addressed this vulnerability through careful climate control and possibly consolidation of the paint layers.