Yseult Riopelle, Jean-Paul Riopelle, Catalogue raisonné des estampes, Hibou Éditeurs, Montréal, 2005, p.204, reproduit en couleurs sous la référence 1970.10EST.L

In the 1970s, and after more than twenty years dedicated to abstraction, the theme of the owl comes back in force in the art of Riopelle as well as figuration in general. He treats them through works on paper, such as Les hiboux, 1970; paintings on canvas, such as Hibou jet-black, 1970; and sculpture, such as Hibou-Roc, 1969-1970 (cast iron in bronze, 2010), demonstrating Riopelle’s incredible talent in a variety of media.

Source: François-Marc Gagnon: Jean-Paul Riopelle, son vie son oeuvre, Institut de l'art Canadien https://www.aci-iac.ca/en/bookss-dart/jean-paul-riopelle/laboures-phares/les-hiboux/

The HC is the inscription on the lithographic works of Jean-Paul Riopelle meaning non-commercial ( hors commerce). The prints of Jean-Paul Riopelle were, for the great majority, published on a number of 75. However, a few more were created and not intended for sale. These non-commercial works were intended to be offered to collaborators of his edition. These collaborators could be master engravers or people close to the artist’s entourage.