Seventy-one studies of flowers and shells similarly signed are in the Fondation Custodia, Institut Néerlandais, Paris (Vermeer and the Delft School, exhib. cat., New York, The Metropolitan Museum of Art, 2001, cat. 96-98). Two other drawings of shells with the same monogram are in the Abrams collection (Bruegel to Rembrandt. Dutch and Flemish Drawings from the Maida and George Abrams Collection, exhib. cat., London, British Museum and elsewhere, 2002-3, cat. 102a-b).