Etching with aquatint by Hans Arp, an artist proof signed and denoted e.a. From the 1966 edition of the book Anthology of Contemporary Engraving. The Forerunners of the Avant-Garde. Vol II. Edited by Arturo Schwarz. Milano, Galleria Schwarz. This exemplar bears the feature of being signed and denoted in vertical and not in horizontal as in the numbered edition.