The glass reproduces an engraving by Michel Natalis (Liège, 1610-1668), which, in softened, classical forms, depicts the reliquary bust of Saint Lambert in the Treasury of Liège Cathedral. This is an outstanding piece of Late Gothic jewellery in embossed and gilded silver, 160 cm tall, made in 1512 by the goldsmith Hans von Reutlingen. It was commissioned by the Prince Bishop of Liège, who is shown in prayer on the base. It is interesting to see how the original is transformed in the graphic version and in the painted version on glass: in both cases the still medieval nature of the original is considerably toned down, eliminating the rich Gothic ornamentation of the niches on the pedestal (with pinnacles, spires and trefoil arches) and the fretwork crowning.