These would seem to have been designed to hold relics of St. Ursula and some of her 11,000 martyred companions, and date from around 1525-1530, possibly from the Low Countries. Another bust, kept at the main branch of the Metropolitan Museum of Art and of a similar appearance and vintage (one of a set of 23) can be seen here.
(images via Flickr. Crossposted to The Shrine of the Holy Whapping.)
