Fold-over mailer with side-open return envelope with slittable edge

Abstract From the Canadian patent

The mailer includes a sheet folded medially to form two plies secured one to another about their marginal edges with an intermediate ply secured about three of its four edges to one of the plies. The remaining edge of the intermediate ply forms an opening for the return envelope defined by the intermediate ply and the one ply. To enable the edge of the return envelope to be slit by automatic mail opening equipment, the intermediate ply is reversely folded along the one edge and adhesively secured to the one ply along the flap. This enables a slit to be formed very close to the edge of the return envelope whereby the return envelope may be opened without interference from the glue line …