Although these two reliefs both depict stories concerning Hercules, they are based on different types of source, which also date from different periods. The representation of Hercules and Antaeus is copied from a small bronze made around 1510 by Peter Vischer the Elder, of which the most celebrated version is in the Bayerisches Nationalmuseum in Munich (Weihrauch, op. cit., p. 271, fig. 321). The scene of Hercules and Omphale, by contrast, is based on a painting by Bartholomäus Spranger, executed for the Emperor Rudolph II in the mid 1590's, and now in the Kunsthistorisches Museum in Vienna (Vienna, loc. cit.). Although the figure of Hercules is changed, Omphale with the humiliated hero's club is identical.